Ministry of Education and Science of the Russian Federation

Federal State Educational Institution

secondary vocational education

"Cherepovets Forestry Mechanical College named after. V.P. Chkalov"

Specialty 140613: "Technical operation and maintenance of electrical and electromechanical equipment"

Course project

by discipline « Electrical and electromechanical equipment"

Subject: " Overhead crane electrical equipment project»

Introduction

a common part

1 History of electric drive development

2 Characteristics of overhead cranes

Calculation part

1 Calculation of drive mechanism power

2 Selecting a control scheme

3 Selection of control and protection equipment

4 Development of connection diagram

5 Design and purpose of the braking device

Safety precautions when servicing overhead cranes

Conclusion

Literature

1. General part

.1 History of electric drive development

Scientific and technological progress, automation and comprehensive mechanization of technological and production processes determine the continuous improvement and development of modern electronic equipment. First of all, this relates to the increasingly widespread introduction of automated electronic devices using a variety of power semiconductor converters and microprocessor controls. New types of electrical machines and devices, variable coordinate sensors and other components used in electronic devices are constantly appearing.

The expansion and complication of the functions performed by electronic devices, the use of new elements and devices in them, and the increasingly widespread inclusion of electronic devices in process automation systems require a high level of training of specialists involved in their design, installation, commissioning and operation.

The history of electric motors usually begins with the development by Russian academician B. S. Jacobi of the first direct current motor for rotational motion. The installation of this engine on a small boat, which made test voyages along the Neva in 1838, is the first example of the implementation of an electric motor. Subsequently, EP began to be used, for example, for aiming an artillery mount, moving the electrodes of an arc lamp, and driving a sewing machine. However, due to the lack of economical sources of direct current electricity, electric drives were not widely used for a long time and the main one was a thermal drive. The creation of an industrial direct current electric generator in 1870, as well as the emergence of a single-phase alternating current system, did not radically change this situation.

The impetus for the development of electric power was the development in 1889 by M. O. Dolivo-volunteer of a three-phase current system and the emergence of a three-phase asynchronous electric motor, which created the technical and economic prerequisites for the widespread use of electrical energy, and therefore electric power.

The first scientific work on the theory of electric drives was the article “Electromechanical Work” by the Russian engineer D. A. Lachinov, published in 1880 in the journal “Electricity,” in which the advantages of the electrical distribution of mechanical energy were shown on a scientific basis. In modern industrial and agricultural production, in transport, in construction, and in everyday life, various technological processes are used, for the implementation of which thousands of different machines and mechanisms have been created by man.

The electrification of our country and the widespread use of electric drives in the national economy began after the adoption and implementation of the state plan for the electrification of Russia - the GOELRO plan, which provides for the widespread construction of new and reconstruction of old power plants, the construction of new power lines, and the development of the electrical industry.

The further development of electrification and automation of technological processes, the creation of high-performance machines, mechanisms and technological complexes is largely determined by the development of the electric drive.

At the same time, further development of the theory of electric drive took place. For the first time, as an independent discipline, the theory of electric drives was presented in the book by S. A. Rinkevich “Electrical distribution of mechanical energy,” published in 1925.

The possibilities for using modern electronic devices continue to constantly expand due to advances in related fields of science and technology - electrical engineering and electrical apparatus engineering, electronics and computer technology, automation and mechanics. This widespread use of electric drives is explained by a number of its advantages compared to other types of drives: the use of electrical energy, its distribution and conversion into other types of energy, the diversity of design, which allows rational connection of the drive with the executive body of the working machine.

The main directions of development of modern digital electronics include:

─ Development and production of complete adjustable electric drives using modern converters and microprocessor control;

─ Increasing operational reliability, unifying and improving the energy performance of electric power plants;

─ Expanding the scope of application of adjustable asynchronous electric motors and the use of electric motors with new types of motors, namely linear, stepper, valve-type, vibration, high-speed, magnetohydrodynamic and others...

─ Development of research work on the creation of mathematical models and algorithms for technological processes. As well as computer design tools for electronic design;

─ Training of engineering, technical and scientific personnel capable of designing, creating and operating a modern automated electric drive.

Solving these and a number of other problems will significantly improve the technical and economic characteristics of electronic devices and thereby create the basis for further technical progress in all sectors of industrial production, transport, agriculture and everyday life.

1.2 Characteristics of overhead cranes

An overhead crane is a crane in which the load-bearing structural elements rest directly on the crane runway.

The overhead crane in the CRG is installed inside the production building and is designed for lifting, lowering and moving various loads during installation, repair and loading and unloading operations. Overhead cranes are called by the distinctive design of longitudinal (main) and transverse (end) beams, made in the form of a bridge; Longitudinal and transverse beams welded together move along a rail track laid on crane beams mounted on the consoles of the columns of the building (workshop, building) or open platform overpass.

Metal bridge structures are made of two- or single-beam. The greatest use is found in two-beam bridges. The overhead overhead crane moves on rails laid on metal or reinforced concrete crane beams supported by building columns or an open overpass. The overhead overhead crane moves along the lower flanges of I-beams secured under the lower chords of the building's construction trusses.

The main parameters of overhead cranes include: load capacity, bridge span, lifting height, lifting speed, crane travel speed, load trolley travel speed, crane weight.

Electrical equipment of overhead cranes is divided into main and auxiliary by purpose. The main equipment is the electric drive, the auxiliary equipment is the equipment for working and repair lighting, alarms, and measuring equipment.

The main electrical equipment of overhead cranes includes:

asynchronous electric motors of three-phase alternating current;

electric motor control devices - controllers, command controllers, contactors, magnetic starters, control relays;

devices for regulating the rotation speed of electric motors - ballast resistors, brake machines;

brake control devices - brake electromagnets and electrohydraulic pushers;

electrical protection devices - protective panels, circuit breakers, maximum current relays, minimum voltage relays, thermal relays, fuses and other devices that provide maximum and zero protection of electric motors;

mechanical protection devices - limit switches and load limiters that protect the crane and its mechanisms from moving to extreme positions and overloading;

semiconductor rectifiers;

apparatus and instruments used for various switching and control

To drive mechanisms on overhead cranes, three-phase AC asynchronous electric motors with both squirrel-cage and wound-rotor crane designs are mainly installed. These electric motors are characterized by increased overload capacity both mechanically and electrically. The multiplicity of the maximum torque of these electric motors in relation to the rated one in repeated short-term mode with a duty cycle of 25% is 2.5-3. These electric motors are manufactured in a closed design, with external airflow and with anti-damp insulation.

Controllers on overhead cranes are designed to control the operation (starting, stopping, regulating rotation speed, changing the direction of rotation) of electric motors.

Power controllers KKT and magnetic remote controls are used. Magnetic controllers are used in electrical equipment of overhead cranes to control the electric drive from a distance. All switching in them is carried out using contactors. The magnetic controller has a number of advantages over the power controller. A magnetic controller of any power is controlled using a small-sized command controller without the use of significant force by the driver (crane operator).

Contactors of magnetic controllers are more wear-resistant than contacts of cam controllers. The use of magnetic controllers allows you to automate the operations of starting and braking the engine, which simplifies drive control and protects the engine from overloads. The set of magnetic controllers for three-phase AC asynchronous motors with a wound rotor includes a command controller, a contactor panel and ballast resistors. Unlike the power controller, the command controller) does not have contacts designed to carry large currents. Instead, contact bridges are used.

In the electric drive of overhead cranes, three-pole contactors are also used to close and open power electrical circuits.

To start, stop and reverse asynchronous electric motors of three-phase alternating current with a squirrel-cage rotor, as well as for closing and opening (switching electrical circuits), magnetic starters are used in the electrical equipment of overhead cranes. Such starters automatically turn off motors when the voltage drops and do not allow the motor to start spontaneously after voltage is restored.

The electrical equipment of overhead cranes is equipped with relays for various purposes and designs. In the electrical circuits of overhead cranes there are relays: thermal, maximum current, time, intermediate, minimum current, thermal relay.

In the rotor circuit of electric motors, resistors are used for their smooth acceleration, braking and regulation of rotation speed. They are also installed in control and signaling circuits, where they perform the function of limiting voltage or current.

To remove the power (closing) springs of two shoe brakes and release the working mechanisms of overhead cranes, special brake electromagnets and electro-hydraulic pushers are used.

Voltage reduction from 380 V to 24 V or to 12 V to power portable lighting lamps is carried out on overhead cranes using single-phase transformers. To power the electric heaters of the driver's (crane operator's) cabin and lower the load in dynamic braking mode, three-phase transformers are installed on the cranes, providing a voltage reduction from 380V to 36V. The tap also has instrument transformers for connecting ammeters. The direct current required for consumption in the electrical equipment of overhead cranes is obtained by converting alternating current into direct current through rectifiers.

Among the types of electrical equipment used on overhead cranes, a special place is occupied by limit switches, which are directly related to ensuring the safe operation of the cranes. On overhead cranes, switches of the types KU, VK, VU, VPK are used.

To protect electrical equipment and electrical networks from high currents, fuses are provided. On overhead cranes, tubular fuses without filling PR-2 and with filling PN2, NPR, NPN are used.

Prevention of violation of normal operating conditions of the electrical circuits of the crane (overload, short circuit) is carried out using automatic switches.

In addition to electrical devices, for frequent switching of electric drive circuits on overhead cranes, various designs of circuit breakers and switches for periodic switching of control circuits and power circuits are used.

Manual and foot-operated periodic switches are used to disconnect the line contactor and enable control circuits, respectively. Manually operated switches serve as emergency switches and are designated VU. Manually controlled switches are used in some cases in the mode of command controllers.

Wires, cables and cords are used to transmit electrical energy. An insulated wire has conductive conductors enclosed in an insulated sheath (rubber, vinylite, polyvinyl chloride). Cables usually have a protective sealed metal (aluminium, lead), rubber or vinylite sheath. For installation of electrical wiring on overhead cranes, only insulated wire is used. In this case, to protect against mechanical damage, the wires are laid in separate gas pipes, metal sleeves or a braided metal sheath. Cables and wires are divided: by type of insulation - uninsulated and insulated (there are a large number of types of insulation); according to the material of conductive cores - copper, aluminum; according to the shape and design of the conductive core - solid or stranded, round cores, sector or segment cores; by type of protective sheath - cables, leaded, with bare lead sheath, with lead sheath and with armor made of steel tape.

Table 1. Technical characteristics of the overhead crane

2. Calculation part

2.1 Calculation of drive mechanism power

Bridge cranes are equipped with mechanisms for lifting, moving the bridge and moving the trolley.

The objectives of choosing electric motors are to determine the fundamental possibility of operating the engine, ensuring the durability of the engine and satisfactory properties of the mechanism-motor pair, and finding the most economical option.

Initial data required for calculating and selecting the electric motor of the lifting mechanism:

Crane lifting capacity 35 t

Hook weight 1 t

Lifting height 25 m

Lifting speed 12 m/min

Mechanism efficiency at load 0.8

Mechanism efficiency at idle speed 0.35

Winch drum diameter 800 mm

Gear ratio of chain hoist 4

Gear ratio 30

Productivity 200t/hour

Voltage alternating 380 V

Let us determine the static moment when lifting a load using the formula:

where is the load capacity, N; - hook weight, N;

Drum diameter, m;

Efficiency of the mechanism under load;

i p - gear ratio;

Number of chain hoist.

Let us determine the static moment when lowering the load (brake release) using the formula:

(2)

Let us determine the static moment when lifting the hook without a load using the formula:

(3)

where is the efficiency of the mechanism at idle.

Let us determine the static moment when lowering the hook without a load using the formula:

(4)

Let's determine the average equivalent moment using the formula:

Let's determine the engine speed:

(6)

where is the lifting speed, m/min.

Let's determine the average equivalent power using the formula:

(7)

Let's determine the number of cycles in 1 hour using the formula:

Where Q- productivity, t/hour;

G n- load capacity, i.e.

Let's determine the cycle duration:

Let's determine the operating time for one operation using the formula:

where is the lifting height, m;

Lifting speed, m/sec

Let's determine the operating time for one cycle using the formula:

Let us determine the duration of inclusions using the formula:

(13)

Let's recalculate the engine power at PVr = 83.3% to standard, with PVst = 60% using the formula:

(14)

Let us determine the power of the electric motor taking into account the safety factor using the formula:

(15)

where K z - safety factor (K z = 1.05-1.1)

Based on these calculations, we select two electric motors, since the crane has two lifts. We enter the data into a table.

Table 2. Engine technical data

engine's type		p nom, rpm	cos,%M max, Nm

(MTN7112-10-asynchronous crane-metallurgical motor, operating at elevated temperatures, H-class of heat resistance, 7-dimension, 1-series, 1-length, 10-number of poles)

We check the selected motor for overload capacity:

where is the maximum torque of the selected engine, Nm;

M max- maximum torque of the calculated engine, Nm;

M nom- nominal torque

The selected engine is suitable.

Let's build a load diagram.

Figure 1. Load diagram

2.2 Choice control circuits

Control circuits for crane motors can be symmetrical or asymmetrical with respect to the zero position of the power controller or command controller. Symmetrical circuits are used for drives of travel mechanisms, and in some cases, for drives of lifting mechanisms. In such cases, with the same numbered positions of the controller handle, when moving in different directions, the engine operates at similar characteristics. Asymmetrical circuits are used for drives of lifting mechanisms, when when lifting and lowering a load it is required that the engine operate at different characteristics.

Magnetic controllers are used primarily to control heavy-duty crane motors.

The motor stator winding is connected through reversing two-pole contactors KM1 and KM2. Resistors in the motor rotor circuits are output via contactors KM3-KM7. The circuit allows you to obtain: automatic start-up on a natural characteristic as a function of independent time delays created by relays KN1-KN3, the coils of which are powered through a rectifier from the protective panel; work at three intermediate speeds; back braking.

The motor armature circuit includes: an excitation winding, a braking electromagnet coil and four resistance stages designed for starting, braking and angular speed control.

The controller circuit ensures that the engine operates in motor mode and in back-off mode.

Protection of the power and control circuits is achieved using circuit breakers and fuses.

All parameters of the machines must correspond to their operation in both normal and emergency modes, and the design must correspond to the placement conditions.

The rated current of the machine must not be lower than the continuous mode current of the installation, and the device itself must not turn off under the specified technological overloads.

2.3 Selection of control and protection equipment

electric drive overhead crane brake

To ensure trouble-free operation, overhead cranes are equipped with instruments and safety devices: limit switches; buffer devices; load limiters or mass measuring devices indicating the mass of the load being lifted; locking devices; devices that prevent collisions between cranes that operate on the same crane tracks; devices to prevent slings from falling out of the cargo hooks; sound and light alarms and means of collective protection against electric shock; brand key.

Limit switches are used to automatically disconnect the load lifting mechanism from the electrical network when the hook suspension approaches the main beams of the bridge, as well as when approaching the end stops of a crane or cargo trolley at a rated speed of more than 32 m/min. After stopping the mechanism, the limit switch should not prevent the mechanism from moving in the opposite direction.

Buffer devices are designed to soften the possible impact of an overhead crane or its trolley on the stops, as well as cranes against each other. The buffer contains an elastic element that absorbs the kinetic energy of the progressively moving masses of the crane or trolley at the moment of impact.

The load limiter is used to turn off the drive electric motor of the load lifting mechanism if the weight of the load being lifted exceeds the rated load capacity of the crane by 25%.

To determine the mass of the cargo being transported by a crane, a mass measuring device is used.

Electrical and electromechanical interlocking devices serve to increase the safety of overhead crane operation. Such interlocks include: mechanical interlocking of the input switch with a brand key, electromechanical interlocking of the cabin door, overhead hatch, zero interlocking.

To select protection devices, I find the rated current of the load-handling mechanism motors using the formula:

(16)

Where R- engine power, W;

U- voltage, V;

cos-Power factor.

I choose a circuit breaker.

All parameters of the machines must correspond to their operation in both normal and emergency modes, and the design must correspond to the placement conditions.

The rated current of the machine must not be lower than the continuous mode current of the installation, and the device itself must not turn off under the specified technological overloads.

Protection of the installation against current overloads will be ensured if the rated current of the circuit breaker with a thermal release is equal to or much greater than the rated current of the protected object.

The thermal and maximum current protection settings for electric motors must correspond to the levels of the corresponding motor currents. The overcurrent protection should not operate when starting the engine, for which its setting current is selected according to the ratio .

Overload protection (thermal protection) is considered effective when

the following relationship between its setting current and the rated current of the motor.

For engine

Setting current of the electromagnetic release

For engine

I enter the circuit breaker data into a table.

Table 3. Technical data of the circuit breaker

I choose a fuse to protect against short circuits.

Table 4. Fuse technical data

I select contactors based on the voltage in the power part of the circuit. I enter the data into a table.

Table 5. Technical data of contactors

Choosing package switches

They are selected according to the type and magnitude of voltage, load current, the number of switchings that they allow under the conditions of mechanical and electrical wear resistance, as well as design.

Table 6. Technical data of package switches

I choose a cam controller of the KKT-60A series to control an asynchronous motor with a voltage of 380V. It has up to 12 power contacts for rated currents up to 63A, as well as low-power contacts for switching control networks.

Control circuit

I accept a control circuit current of 10A.

I choose a command controller for switching several low-power electrical circuits.

Table 7. Technical data of the command controller

Selecting control buttons

Table 8. Technical data of control buttons

I choose magnetic starters designed for starting, stopping and protecting asynchronous electric motors.

Table 9. Technical data of magnetic starters

Choosing an incandescent lamp

Table 11. Technical data of lighting lamps

.4 Development of connection diagram

Table 13. Development of connection diagram

Device name	Device location	Symbol
Input switch SF	In the protective panel
Fuses	In the protective panel
Limit switch SQ1- SQ5	In the power circuit
Buttons SB1-SB6	In the crane operator's cabin
Electric motor M	In the power circuit
Contactor KM	In the protective panel
Forward contactor KM3	In the protective panel
Contactor “back” KM4	In the protective panel
Circuit breaker QS	In the protective panel

.5 Design and purpose of the braking device

Electric overhead cranes use block and disc brakes. In shoe brakes, the brake shoes are pressed against the outside surface of the brake pulley. In disc-pad brakes, the brake pads are made flat and they are pressed against the end surfaces of the disc. The brakes of overhead cranes are closed, i.e. their pads are pressed against the brake pulley or disc in the normal state when the drive motor of the mechanism and the brake drive are turned off. The brake closing force (the force of pressing the pads against the pulley or disc) is created by a constantly acting external force of a pre-compressed closing spring. These brakes open, releasing the crane mechanisms, only when the brake drive is turned on simultaneously with the mechanism's drive motor being turned on. Crane brakes are activated automatically when the drive motor of the mechanism is turned off. The brakes of overhead crane mechanisms do not create resistance forces during operation of the mechanism, but stop the mechanism only at the end of movement when the drive electric motor is disconnected from the electrical network and hold the mechanism in place when parked.

The action of crane brakes is based on the use of frictional forces that arise when stationary pads are pressed against a rotating brake pulley or disc. The value of the friction force created in this case depends mainly on the force of pressing the pads against the brake pulley and the coefficient of friction between the pulley and the pads. The pad is pressed against the brake pulley under the force of the closing spring. This force depends on the degree of compression, i.e. spring settlement, and the length of the spring in the compressed state. By adjusting the length of the spring in the compressed state, you can increase or decrease the force of pressing the pads against the brake pulley.

The coefficient of friction depends on the properties of the materials from which the brake pads and pulley are made, as well as on the condition of the friction surface of the brake pulley - the presence of lubricant, moisture, rust, marks and grooves. To increase the stability of the friction coefficient and increase the service life of the brake, brake pulleys are subjected to heat treatment, most often with high-frequency currents to a given hardness. Brake pads are equipped with friction linings made from a mixture of asbestos wool with various rubbers or resins. Such linings have a stable and high friction coefficient. Thus, during operation of the brake, the friction force is created when the friction linings are pressed against the heat-treated friction surface of the brake pulley.

When braking, the kinetic energy of the moving mechanism is converted into thermal energy by heating the brake surface. In heavy and very heavy operating modes of cranes, the temperature of the brake friction surface can reach 200°C or more. One of the disadvantages of the friction linings of crane shoe brakes is that with strong heating, the coefficient of friction of the lining on the pulley begins to decrease. In this case, the friction force decreases proportionally and the braking distance increases, which can lead to a crane accident. For this reason, the overhead crane cannot be used in a mode more severe than the mode specified in its passport. Friction linings wear out quickly if the force of their pressing against the brake pulley exceeds a specified value.

When a brake operates, a braking torque occurs as a result of frictional forces. The braking torque depends on the friction force and the diameter of the brake pulley. With an increase in the diameter of the pulley, under the same conditions of pressing the pads against the pulley and the coefficient of friction, the braking torque increases. Therefore, different crane mechanisms have brakes with different brake pulley diameters.

Depending on the speed at which braking begins, the braking torque and the mass of the crane or the load being lifted, the cargo trolley, crane or load, when braking, will travel a certain distance, which is called the braking distance, until it comes to a complete stop.

The electro-hydraulic pusher, which drives the brakes, consists of a housing in which the cylinder is installed. Below the cylinder there is a pump with a drive electric motor. The electric motor is asynchronous, three-phase, flange type with a squirrel cage rotor, power 0.2 kW. A pump wheel with a centrifugal pump impeller is mounted on the electric motor shaft. The impeller design uses straight radial blades, which ensure normal operation of the pusher regardless of the direction of rotation of the electric motor shaft. The motor frame is bolted to the motor housing. The connectors are sealed with rings made of oil-resistant rubber; a seal is also provided to prevent oil from flowing through the rod. Oil is poured into the electric motor through a hole closed with a plug, and drained through a hole located at the bottom of the frame. The internal cavity of the pusher is filled with transformer oil, after which, to remove air, it is necessary to close the plug and turn on the pusher five times under a load on the rod of 100-250 N. Then the oil is added until it begins to flow through the filling channel. If there is no power in the stator winding of the electric motor of the hydraulic pad pusher, under the action of a spring through the rod, the upper lever and the rod transmit force to the lever. The levers, turning on their fingers, tightly press the pads to the surface of the brake pulley, creating the necessary friction force. When the mechanism is turned on, the electric motor of the electric hydraulic pusher also turns on. After turning off the electric motor of the hydraulic pusher, the spring again presses the pads to the pulley.

The advantages of electrohydraulic pushers in comparison with electromagnets include the ability to regulate the brake response time, a smooth increase in braking torque, a large number of activations, high durability, ease of operation, noiselessness, etc.

3. Safety precautions when servicing overhead cranes

Safe operation of load-lifting cranes can be ensured by complying with the requirements of safety regulations. The organization of a service for compliance with labor safety requirements during the operation of cranes must be carried out in accordance with SNiP 12-03-99 “Labor safety in construction. Part I. General requirements”, “Rules for the design and safe operation of load-lifting cranes”. The company operating the crane appoints those responsible for the safe performance of work on moving cargo with cranes at sites.

The company that owns the crane agrees on the work plan for installing the crane at the site; conducts partial and complete technical examination of the crane; periodically checks (inspects) the condition of the crane and supporting base; checks compliance with the procedure established by the Rules of the State Mining and Technical Supervision of the Russian Federation for admitting workers to operate and maintain the crane; participates in commissions for certification and periodic testing of knowledge of labor safety requirements for the driver (crane operator) and maintenance personnel, takes measures to comply with labor safety requirements when operating the crane and troubleshooting its components and assembly units; appoints a driver (crane operator) to work on the crane and provides him with production instructions for the safe conduct of work.

The enterprise operating the crane provides the facility with a work execution plan (WPP); compiles a list of measures taken to ensure safe work in the crane operating area; arranges crane tracks for crane movement near the structure under construction; checks the technical examination of removable load-handling devices and their markings; appoints slingers to strap and hook loads when moving them by crane; determines and indicates to the driver and slingers the place and procedure for safe storage and installation of structures; instructs the driver (crane operator) and slingers on the safe performance of the upcoming work; does not allow installation and loading and unloading work with cranes near the power line without a permit; ensures lighting of the work site at night in accordance with the standards; does not allow unauthorized persons into the working area of ​​the crane; ensures the safety of the crane at the end of the shift.

The Installation Instructions indicate at what wind speed the installation and dismantling of the crane should be stopped. It is prohibited to carry out installation work at heights when there is ice, at night, during thunderstorms, fog and at air temperatures below -20° C. Installation at night is only possible in case of an accident. It is prohibited to lower or raise the tower at night. When working in the dark, the installation site must be illuminated. In case of ice, the installation site should be sprinkled with sand. The crane is cleared of snow and ice before lifting. The use of ice-covered ropes for slinging is not allowed. Only installers who have the appropriate certificate are allowed to operate the crane mechanisms during installation. When installing and dismantling the crane, it is prohibited to: fasten structural elements with an incomplete number of bolts; install a crane near a pit with unreinforced slopes; carry out any work in the installation or dismantling area that is not directly related to installation.

To reduce the impact of dangerous and harmful production factors, the operator (crane operator) must perform work on moving cargo by cranes, maintenance and repair using personal protective equipment. The main means of protection against industrial pollution and mechanical damage is workwear: a suit for men or women, consisting of a jacket with trousers or overalls. Special shoes are designed to protect the driver’s feet from cold, mechanical damage, oil, etc. For outdoor work in winter, the driver (crane operator) wears a cotton jacket, trousers and felt boots, which he hands over for summer storage in the spring. To protect hands from mechanical damage when carrying out maintenance and repair work on the crane, the operator must use special gloves. A helmet is necessary to protect the head from mechanical damage and electric shock. The driver (crane operator) is given a dark or orange helmet. White helmets are intended for managers. Helmets may be equipped with noise protection devices. When working at height, the driver (crane operator) must use a safety belt.

Before starting work, the driver (crane operator) inspects the crane, checks the serviceability of the brakes and safety devices, gets acquainted with the working area at the site and installs the crane in it in accordance with the work project, checks the serviceability of the crane tracks and load-handling devices; determines the labeling of transported goods, becomes familiar with dangerous goods and substances. The driver (crane operator) participates in EO1) looks at the entries in the logbook and, if possible, eliminates the crane problems recorded in this log or reports them before starting work to the person responsible for the good condition of the crane. It is prohibited to start work if malfunctions are identified: cracks or deformation in the load-bearing metal structures of the crane, loose clamps in places where ropes are attached, excessive wire breaks or surface wear, damage to the brake parts of the cargo winch and safety devices.

Before starting the crane, all fixtures, tools and loose parts are removed from it; make sure that counterweight and ballast plates and rail anti-theft grips are installed correctly and securely; remove people from crane tracks.

During work, the driver (crane operator) does the following:

does not allow unauthorized persons onto the tap;

checks the slope of the site on which the crane stands; a slope of no more than 3° is allowed;

maintains the distance from the edge of the pit or trench to the nearest support (wheel, track, outrigger) of the crane;

performs working movements at the signal of the slinger;

controls the weight of the lifted loads and the reach using an indicator in the cabin or mounted on the boom);

before lifting the load, warns the slinger and everyone near the crane about the need to vacate the working area of ​​the crane;

installs the load-handling device so as to eliminate oblique tension of the cargo rope (when lifting the load, the distance between it and the hook suspension should be 0.5 m);

lifts loads moved horizontally 0.5 m above objects encountered along the way; monitors the absence of people in the gap between the lifted or lowered load and protruding parts, buildings and vehicles;

pauses the operation of the crane when the rope is laid unevenly or falls off the drum.

Prohibited:

without a permit, install a crane or move a load closer than 30 m from the outermost wire of an existing power line;

simultaneously operate the two lifting mechanisms available on the crane (main and auxiliary);

carry out work movements in an explosion- and fire-hazardous area without the presence of the person responsible for moving goods by cranes;

allow workers who do not have slinger rights to strap and hook loads;

lift loads of unknown mass;

lift lifting devices pinched by loads and reinforced concrete products with damaged hinges.

Moving cargo with an electromagnetic plate is permitted only in specially designated areas of the warehouse (cargo processing point). When unloading vehicles, it is not allowed to move the electromagnetic plate with a load above the vehicle cabin, and when unloading railway cars - above the train. It is necessary to constantly monitor the correct winding of the lifting electromagnet cable onto the drum. The driver has no right to leave the cab if there is a load on the electromagnetic plate. When working with the grab, you must ensure that the jaws close tightly. Do not allow the load rope to become too loose and come out of the drum channel.

When a thunderstorm and hurricane winds approach, the load is lowered and work is stopped.

At the end of the shift, the driver (crane operator) is obliged to: not leave the load hanging; place the tap in the designated place and secure it; stop the power plant and, when powering the tap from an external source, turn off the switch; inform your shift worker about any malfunctions in the operation of the crane and make an appropriate entry in the logbook. When working in cramped conditions, observe the restrictions on the working movements of the crane and display warning and prohibiting safety signs.

The person responsible for the safe performance of work at the construction site and the engineering and technical worker supervising the safe operation of the cranes ensure timely notification of the driver (crane operator) about sudden changes in weather (blizzard, hurricane wind, thunderstorm, heavy snowfall). The crane must not be left unattended with the power unit running and the cabin doors open.

Maintenance (MOT) of cranes on a construction site has to be performed in the absence of permanent jobs and in various weather conditions. This represents increased requirements for ensuring safe working conditions. To perform maintenance, select a flat (to exclude the possibility of spontaneous movement of the machine under the influence of gravity) free from foreign objects area with a hard non-slip coating at a distance of at least 50 m from the storage areas of petroleum products. Chocks are placed under the wheels of the cranes, and the booms are lowered all the way. Electrical taps are de-energized and warning signs are posted. Use only serviceable tools, jacks and fixtures. Tools, spare parts, and accessories must be lifted onto the crane only in a special bag or using a rope. Assembly units and components are installed on stands and trestles, tested for load capacity. Maintenance operations with running wheels are carried out after releasing air from the chambers. When washing a faucet with a high-pressure jet, flying dirt can get into your face and eyes. Assembly units are cleaned with compressed air using safety glasses. When refueling the crane, the driver (crane operator) stands so that the wind does not blow vapors and splashes of fuel onto him. The operation is performed using gloves. When adding water to the cooling system, open the radiator cap slowly so that steam comes out gradually to avoid being burned by the hot steam on your face and hands. In winter, metal buckets with a nozzle that allows you to direct the stream of water are used to fill hot water. The use of homemade buckets (for example, made from rubber tubes) is prohibited. When using steam to heat engines, precautions must be taken. The steam hose is inserted into the neck of the radiator and secured to prevent it from falling out. The oil in the crankcase and the working fluid in the hydraulic equipment are in a hot state when the valve is operating, so they are carefully drained into special containers.

To prevent spontaneous opening of cabin doors, the locks must be in good working order. Cabin doors must close tightly, as dust leaks through the openings and pollutes the air. Particular attention is paid to the presence of covers in the places where the levers and pedals pass. The seat cushion and backrest are kept in good technical condition, with no dips, protruding springs or sharp edges.

Load-lifting cranes have an electric drive and belong to electrical installations with a voltage of 1000 V. “Rules for the technical operation of electrical installations of consumers” and “Safety rules for the operation of electrical installations” of consumers require that operators of overhead and electric load-lifting cranes have certain knowledge of electrical engineering and electrical equipment of cranes, know and knew how to provide first aid in case of electric shock. The human body is a good conductor of electric current; depending on many reasons and conditions, the effect of electric current can be from a slight, barely noticeable convulsive contraction of the muscles of the fingers, to the cessation of the heart or lungs, i.e. fatal defeat.

Electric shock occurs when an electrical circuit is closed through the human body, so the driver (crane operator) must be provided with protective equipment. According to the degree of reliability, insulating protective equipment is divided into basic and additional. The main ones are those protective equipment whose insulation can reliably withstand the voltage of the installation and through which direct contact with live parts under voltage is allowed. Additional are protective equipment that serves to enhance the effect of basic equipment and to protect against touch voltage and step voltage. In crane electrical installations, the main protective equipment is insulating gloves, and additional equipment is insulating overshoes and mats. In case of electric shock, it is necessary to free the victim from the action of the current as soon as possible, since the severity of the electrical injury depends on the duration of this action. It must be remembered that you can only touch a live person if you take the necessary precautions. First aid measures will depend on the condition of the victim after he is released from the electric current.

Conclusion

I have developed a project for electrical equipment for an overhead crane with a lifting capacity of 35 tons.

The general part of the course project indicates the basic requirements for the electrical equipment of a crane, which is intended for lifting operations. With the help of an overhead crane, high production rates are achieved. It provides servicing of a large working area equal to the travel of the cargo trolley multiplied by the length of the crane runway.

In the calculation part of the project, the power of the electric motor of the lifting mechanism was calculated and selected. A verification calculation of the power circuit elements was carried out. Protection and control equipment has been selected.

The selected electrical equipment complies with the PUE standards.

Switching equipment can protect consumers from overload and short circuits.

The “Safety” section describes safety issues when servicing the crane.

I believe that the electrical equipment I have chosen will reduce downtime during operation of the crane, improve operational properties and increase reliability and safety of operation.

Literature

1. Aleksandrov K.K., Kuzmina E.G. Electrical drawings and diagrams - M.: Energoatomizdat, 1990, 288 p.

Barybin Yu.G., Fedorov L.E. Handbook on power supply design - M.: Energoatomizdat, 1990, 576 p.

Karpov F.F., Kozlov V.N. Handbook for calculation of wires and cables - M.: Energy, 1969, 264 p.

Zimin E.N. Electrical equipment of industrial enterprises and installations - M.: Energoatomizdat, 1991

5. Interindustry rules for labor protection (safety rules) during the operation of electrical installations - St. Petersburg: DEAN Publishing House, 2001, 208 p.

6. Pizhurin P.A. Handbook of an electrician for a logging enterprise - M.: Forestry Industry, 1988, 363 p.

Pizhurin P.A. Electrical equipment and power supply of timber and wood processing enterprises - M: Forestry Industry, 1993, 263p.

Rules for the design of electrical installations - M.: Glavgosenergonadzor of Russia, 2001, 6th edition.

Rules for the construction of electrical installations - St. Petersburg: DEAN Publishing House, 2002, 928 p.

Overhead crane is a crane with a load-handling device suspended from a load trolley or hoist that moves along a movable steel structure (bridge). Thanks to its design, an overhead crane can move a load to any point in the working area limited by the lengths of the crane and span beams.

An overhead crane can be divided into two main groups of elements: mechanical components And electrical equipment, allowing you to control the operation of the crane.

Mechanical components of an overhead crane

Crane bridge, which also has another name - span beam- This is the supporting structure of the crane, designed for the movement of a cargo trolley along it. The crane bridge consists of one or two span beams connected to end beams, which in turn can move the entire overhead crane structure along the crane beams. One or two load trolleys can be located on the crane bridge, on one or two independent tracks.

Or simply crane trolley designed to move and lift loads along the span (span beam of an overhead crane). The design of the trolley is a frame welded from transverse and longitudinal beams, which rests on running wheels and has a very rigid structure. On the frame of the trolley there is a lifting mechanism (auxiliary and main lifts), a mechanism for moving the trolley itself along the crane bridge, a pantograph, as well as safety devices. A hoist or hoist is installed on single-girder overhead cranes; a double-girder crane is equipped with a load trolley.

Tal or telpher– suspended lifting device with manual or mechanical drive (usually electric). Hoists are widely used both as an independent lifting mechanism and in trolleys of single-girder overhead cranes.

Electrically driven hoist (telpher) It is a winch with a gearbox, electric motor, drum or sprocket, brake and hook suspension. There are stationary and mobile (mechanized) hoists, suspended from special carts moving along suspended monorail tracks.

End beam is an integral part of the overhead crane and performs the functions of a mechanism for moving the crane bridge along the crane tracks located perpendicularly and at the same time serves as a bridge support. The end beam consists of a body, wheel blocks and a gear motor. The end beams included in the overhead crane are usually called a set of end beams.

Runway serves to move the overhead crane along the crane beam. For an overhead crane, the crane runway can be made supporting (for supporting overhead traveling cranes) and suspended (for suspended overhead traveling cranes). Depending on this, the crane runway can be of two types: rail or beam. The rails used are square or strip steel, railway rails or special crane rails.

Crane beams– this is the main load-bearing element of the crane structure, which receives and transmits crane loads to a fixed base and ensures safe operation of the crane along the entire path of its movement. There is a crane runway on the crane beam. Crane beams can be made of metal beams or reinforced concrete. Crane beams are a structural element of a crane trestle.

is a global engineering structure consisting of supports and a span horizontal structure, which is the supporting structure for an overhead crane. The crane trestle can be installed in a production area or in the open air.

The built-in type crane trestle is used in production facilities or workshops and is installed on supports. Workshop columns can be used as supports, on which crane beams are installed. Also, the crane trestle can have an independent design. In this case, columns or trusses made of metal structures with a flanged base are used as supports.

On open sites, in the open air, an open crane rack is installed. The columns of the overpass are installed on their own foundation.

In accordance with the Rules, for convenient and safe maintenance of cranes, their mechanisms and electrical equipment located outside the cabin, the design of overhead cranes provides for the installation of appropriate galleries, sites And stairs.

According to the type of crane bridge suspension, overhead cranes are divided into supporting And hanging.

Support overhead crane is a crane whose end beam rests on the crane track rails located on top of the crane beam.

Overhead overhead crane- this is a crane, the end beam of which is attached to the crane runway, located on the lower belt of T-beams or I-beams.

According to the number of span beams, overhead cranes are divided into single beam And double beam. Accordingly, the overhead crane has either one or two spans. Double girder cranes are more stable, have a more even load distribution and can lift more weight.

Control cabin is located on the crane bridge in a place that provides the best visibility and safety for the crane operator; most often it is located at the edges or in the middle of the crane bridge span. Sometimes the control cabin is suspended from a cargo trolley. In some cases, to improve visibility, the cabin has the ability to move autonomously along the crane span.

Electrical equipment of an overhead crane

Electrical equipment of an overhead crane is divided into basic, ensuring the movement of the bridge and the cargo trolley and the lifting/lowering of the load, and auxiliary, performing various additional functions not directly related to the main operation of the crane.

Basic equipment

• AC electric motors;
• control systems - controllers, contactors, control relays, magnetic starters, switches and other equipment that allows you to control electric motors;
• electromagnets, electrohydraulic pushers and other devices that ensure the operation of locking brakes;
• circuit breakers, fuses, current relays and other electrical protection devices;
• load limiters, end position limiters and other mechanical safety devices.

Auxiliary equipment

• additional lighting equipment;
• sound alarm devices;
• heating devices (electric furnace in the crane control cabin);
• measuring equipment;
• additional protection.

Power supply of mechanisms

Power supply to the crane elements can be carried out in two ways: trolley lines or daisy chain cable systems.

The design of an overhead crane includes such elements of electrical equipment as an electrical cabinet, control panel, conductor, etc.

- this is a metal box that contains the electrical equipment of the crane - controllers, contactors, control relays, magnetic starters, resistors, frequency converters, switches and other equipment that allows you to control electric motors.

The overhead crane can be controlled by a console (the operator controls the crane using a control panel from the floor) or from a control cabin installed on the overhead crane. Depending on this, the overhead crane can be equipped with either a control panel or a control cabin.

Remote Control is a device for monitoring and controlling crane equipment. Control panels are divided into pendant consoles And radio remote controls.

Control pendant can have independent movement along the span, suspended from the electrical cabinet, or move together with the crane trolley along the crane bridge.

Radio remote control controls the crane via a radio communication channel and is not connected to the crane by wires.

Conduit for an overhead crane, it ensures the supply of electricity from the network to the moving crane, as well as its mechanisms. There are two types of conductors - trolley and flexible.

Trolley conductor to the overhead crane is carried out using rigid trolleys and pantographs that slide along them when the crane moves. But most often, due to the simplicity and cost reduction of the design, a current supply with a flexible cable is used - daisy chain conductor. A conductor with a flexible cable (daisy-chain type) is often used to power cargo trolleys and is mandatory when operating cranes in fire and explosive environments.

Bridge type. In the 2000s, their production in Russia decreased to 1000-1500 units of equipment.

The simple design of the overhead crane allows for widespread use G ruzo P detachable m tires (GPM) of this type in enterprises of various sizes - from small auto repair shops to large metallurgical plants or thermal power plants.

Are used pavements taps in order to lift and move heavy loads large sizes in everyone areas industrial activities person.

The technical characteristics of overhead cranes allow the use of this category of hydraulic lifting machines both for internal loading and unloading and for external work in any climatic conditions.

Flaw pavements GPM- in their stationarity, and plus— is that they can use the building height.

Bridge PMGs are divided into 2 big groups: general appointments And special.

Bridge OPI (general industrial design) are equipped with a load hook.

Special - equipped with grips that have a highly specialized purpose: grab, magnet, grips for containers. Special lifts appointments are made with a rotating trolley or boom.

A separate group includes metallurgical gas-and-metallic machines intended only for this industry. Such GPMs are equipped with special equipment. grips: foundry, forging, for stripping ingots, etc.

Two ways to support a crane runway

An I-beam span has upper and lower horizontal chords. Supporting ones are placed on the upper one, and hanging ones are attached under the lower one:

• Supporting — are installed with wheels on the rails from above. The load-bearing capacity of the support GPM is maximum (up to 500t), but the construction of a crane trestle or supports requires financial costs.
• Hanging — are hooked to the lower shelves of the crane runway. This type of support is easy to install and has a low cost. The small lifting capacity (up to 8 tons) is compensated by the low height of the structure, which is why the size of the working area is larger than that of support cranes.

  Suspended cranes can be installed on part of the workshop. It is possible to dock cranes (butt lock) and move trolleys from one crane to another.

Device designs vary. They can move translationally or make revolutions around the vertical axis (chordates, radials and rotations) of the PMG.

Overhead crane design

Depending on the number of main beams, the GPM design can be:

• single beam. Used in small industries, it can be suspended or supported. G/p<= 10 т.
• Double beam. The design is carried out only in the support version, because their carrying capacity is > 8 tons.

  Use - in large production workshops, in the automotive, metallurgical industries. Span length - up to 60m. A cargo trolley may have an auxiliary lifting mechanism in addition to the main one.

Type of bridge PMG drive

The drive mechanisms of bridge PMGs can be manual or electric.

• Manual drive unit. This overhead crane uses worm hoists as its movement mechanism.

  Manual hydraulic lifting machines are used to lift relatively small loads when performing auxiliary or repair work.

• Electric drive. Electric hoists serve as devices for lifting and moving loads. The PMG bridge also moves with the help of electric motors; they transmit rotation to the running wheels either through gearboxes or through a gearbox and transmission.

What does an overhead crane consist of?

The general structure of an overhead crane is a single- or double-girder bridge and a load trolley that moves along it.

Electrical equipment and main components and mechanisms are placed on the bridge and on the trolley.

Brake system

The standard braking system for bridge PMGs is block or disc-block.

If the trolley speed is ≤32 m/min, the moving mechanisms do not need to be equipped with brakes. Under these conditions, the PMG will be able to brake on its own without exceeding the braking distance.

Functionally, the braking devices of cranes are locking - to stop the device - and release - slowing down the descent.

Brakes can be open or closed types. The lifting mechanisms of cranes are equipped with closed brakes - in the normal position the mechanisms are braked, the brake is released only when the engine starts.

Lifting mechanisms for cranes moving dangerous goods: molten metal, explosives, toxic substances, acids, have 2 brakes that operate autonomously.

Closed type brakes are used in hydraulic and mechanical engineering because they are more durable than open ones and their failure can be easily noticed.

In some cases, open brakes are mounted in addition to closed ones (as auxiliary ones) to increase the speed and accuracy of load placement.

Lifting mechanisms

The mechanism for lifting and lowering the load is also located on the crane trolley.

It consists of a drive electric motor, transmission shafts, a horizontal gearbox and cargo cables with a winding drum.

For work with loads >80 t, additional overhead crane gearbox or reduction gear. To increase the traction force, a chain hoist is used (most often a double multiple).

Overhead crane gearbox, its purpose and design

Functionally, cylindrical crane gearboxes can be divided into:

• lifting gear reducers;
• trolley motion reducers;
• axle motion reducers.

The gearbox may have 2 types of execution: unfolded and planetary.

Reducers of the deployed type, equipped with cylindrical wheels, are more popular. Repair and maintenance of mechanisms of this design are simpler and cheaper.

Crane tracks for overhead cranes

When constructing a crane track, railway rails P18, P24, P38 (narrow gauge) and P43, P50 and P65 (for wide gauge) are used as crane and trolley rails.

They also use special crane rails KR50, KR70, KR80, KRYUO, KR120, or square steel guides with rounded edges (for mechanisms with lifting capacity ≥ 20t).

I-beams are used as crane tracks for suspended type GPM.

Fastenings rails To beams must exclude bias rails and should allow quick replacement of worn rails. Their ends are connected with double-sided plates and bolts or welded.

Electrical equipment

Special, increased requirements are imposed on the electrics of bridge PMGs, which is due to intense operating conditions.

In 1 hour, hundreds of switches on, switch offs and overloads associated with acceleration and braking of the device as a whole or the trolley can be performed.

The movement of the bridge and crane trolley, lifting and moving the load is carried out by the main electrical equipment:

• electric motors. 3 (4) motors are installed, 2 of them are placed on the trolley to lift/lower the load and move the trolley along the bridge beam, and 1 (2) motor moves the crane beam along the rails. In overhead cranes for operational testing, durable asynchronous electric motors are used, designed for frequent overloads and starts of the MT or MTK series (for light work), three-phase current;
• controllers, control relay, magnetic starters and other equipment for controlling electric motors;
• electromagnets, pushers and other devices involved in the operation of holding brakes;
• limiters load capacity and other mechanical protection.

Spotlights, working and repair lighting, heating, sound alarms, measuring equipment - all this is auxiliary electrical equipment.

Power is supplied in 2 ways: trolley lines or daisy chain cable systems:

1. Trolley line— used in heavy-duty hydraulic machines.

The trolley bus must be placed at a height of ≥3.5 m from the floor and at least 2.5 meters to the bridge deck.

1. Cable system. Flexible electrical cable, which is suspended on special cable-carrying carriages. The garland system is cheaper, its installation and operation is easier, but it is less reliable.

A trolley line is used to move the bridge beam, and a cable system is used to move the crane trolley.

Construction of a crane trolley for an overhead crane

The cargo trolley lifts, lowers and moves cargo along the bridge.

Mounted on a rigid steel frame with driving and driven wheels numerous crane nodes.

These are drives, electric motors of lifting mechanisms (main and auxiliary), current collector, lifting height blockers.

An emergency stop of the trolley in the event of a brake system breakdown is provided by buffers.

The cantilever trolley is used for single-beam devices. In double-beam systems, trolleys are used that can move along both belts of beams (lower and upper).

Overhead crane control circuit

The PMG is controlled from a suspended cabin or from a wired (wireless) remote control; the operator is located on the workshop floor (ground) or outside the work site.

Overhead crane installation

Bridge GPM requires improvements to the work site- a crane path needs to be laid.

The rail track can be mounted on a special crane trestle, or the floor, columns and supports of the building are used to construct it.

There are 3 optionsinstallation:

• Element-by-element (step-by-step). The assembly of crane units takes place at the top of the crane tracks.
• Large block — the so-called enlarged assembly. Large fragments (mechanisms, electrical equipment, components) of the crane, pre-assembled below, are raised to the height for installation.
• Full block — complete bridge assembly on the floor. The entire structure is lifted and mounted on the crane tracks. This method requires the use of powerful technology.

Photos of different models

This is what these mechanisms look like at work:

In contact with

Introduction

Cranes are lifting devices used for vertical and horizontal movement of goods over long distances. According to design features related to their purpose and operating conditions, cranes are divided into bridge, portal, gantry, tower, etc. In the workshops of electrical engineering enterprises, overhead cranes are most widely used, with the help of which heavy workpieces, parts and machine components are lifted and lowered, and as well as their movement along and across the workshop. The type of overhead crane is mainly determined by the specifics of the workshop and its technology, however, many components of crane equipment, such as lifting and moving mechanisms, are made of the same type for different types of cranes.

Electric cranes are equipped with electric motors, starting and control resistances, brake electromagnets, controllers, protective, ballast, signaling, blocking and lighting equipment, limit switches, and current collectors. Power is supplied to the crane either through trolley conductors fixedly fixed to building structures and current collectors mounted on the crane, or using a flexible hose cable. Electric motors, devices and electrical wiring of cranes are installed in a design that meets environmental conditions.

Depending on the type of cargo being transported, overhead cranes use various load-grasping devices: hooks, magnets, grabs, pliers, etc. In this regard, there are hook cranes, magnetic cranes, grab cranes, tong cranes, etc. The most widespread are cranes with a hook suspension or with a lifting electromagnet, which are used for transporting steel sheets, shavings and other ferromagnetic materials.

For all types of cranes, the main mechanisms for moving goods are lifting winches and travel mechanisms.

According to their lifting capacity, overhead cranes are conventionally divided into small (load weight 5-10 tons), medium (10-25 tons) and large (over 50 tons).

The movement of goods associated with lifting operations in all sectors of the national economy, in transport and in construction is carried out by a variety of lifting machines.

Lifting machines are used for loading and unloading operations, moving cargo in the technological chain of production or construction, and performing repair and installation work with large-sized units. Lifting machines with electric drives have an extremely wide range of use, which is characterized by a range of drive powers from hundreds of watts to 1000 kW. In the future, the power of crane mechanisms may reach 1500–2500 kW.

Depending on the purpose and nature of the work performed, overhead cranes are equipped with various load-handling devices: hooks, grabs, special grips, etc. The overhead crane is very convenient to use, since due to its movement along the crane tracks located in the upper part of the workshop, it does not occupy any useful space.

The electric drive of most lifting machines is characterized by repeated short-term operation with a higher switching frequency, a wide range of speed control and constantly occurring significant overloads during acceleration and braking of mechanisms. The special conditions for using electric drives in lifting machines formed the basis for the creation of special series of electric motors and crane-type devices. Currently, crane electrical equipment includes a series of AC and DC crane electric motors, a series of power and magnetic controllers, command controllers, push-button posts, limit switches, brake electromagnets and electro-hydraulic pushers, starting-brake resistors and a number of other devices that complete various crane electric drives.

In crane electric drives, various

systems of thyristor regulation and remote control via radio channel or one wire.

Currently, lifting machines are produced by a large number of factories. These machines are used in many sectors of the national economy in metallurgy, construction, mining, mechanical engineering, transport, and other industries.

The development of mechanical engineering, engaged in the production of lifting machines, is an important direction in the development of the country's national economy.

1 BRIEF CHARACTERISTICS OF THE BRIDGE CRANE.

Electric cranes are devices used for vertical and horizontal movement of loads. A movable metal structure with a lifting winch located on it are the main elements of a crane. The lifting winch mechanism is driven by an electric motor.

A crane is a cyclic lifting machine designed to lift and move a load held by a load-handling device (hook, grab). It is the most common lifting machine, which has a very diverse Overhead crane (Figure 1) is a bridge that moves along crane tracks on running wheels that are mounted on end beams. The tracks are laid on crane beams resting on the projections of the upper part of the workshop column. The crane movement mechanism is installed on the crane bridge. All mechanisms are controlled from the cabin attached to the crane bridge. Electric motors are powered via workshop trolleys. To supply electricity, sliding type current collectors are used, attached to the metal structure of the crane. In modern designs of overhead cranes, the current supply is carried out using a flexible cable. The drive wheels are driven by an electric motor through a gearbox and transmission shaft.

Any modern load-lifting crane, in accordance with safety requirements, can have the following independent mechanisms for each working movement in three planes: a mechanism for lifting and lowering the load, a mechanism for moving the crane in a horizontal plane and mechanisms for servicing the crane’s work area (moving the trolley).

Lifting machines are manufactured for various conditions of use:

according to the degree of loading, operating time, intensity of operations, degree of responsibility of lifting operations and climatic factors of operation.

The main parameters of the lifting mechanism include:

lifting capacity, hook lifting speed, operating mode, lifting height of the lifting device.

Figure 1 – General view of the overhead crane

Rated lifting capacity - the mass of the rated load on a hook or gripping device, lifted by a lifting machine.

The hook lifting speed is selected depending on the requirements of the technological process in which the lifting machine is involved, the nature of the work, the type of machine and its performance.

2 OPERATING CONDITIONS AND GENERAL TECHNICAL CHARACTERISTICS OF THE ELECTRICAL EQUIPMENT OF THE BRIDGE CRANE.

The increased danger of work when transporting lifted loads requires compliance with mandatory rules for the design and operation of lifting and transport machines during design and operation. On lifting and moving mechanisms, the rules for design and operation provide for the installation of travel limiters, which affect the electrical control circuit. The limit switches of the lifting mechanism limit the upward movement of the load-handling device, and the switches of the bridge and trolley movement mechanisms limit the movement of the mechanisms in both directions. It is also provided for the installation of limit switches that prevent collision of mechanisms in the case of two or more cranes operating on one bridge. The exception is installations with movement speeds up to 30 m/min. Crane mechanisms must be equipped with closed-type brakes that operate when the voltage is removed.

On crane installations, it is allowed to use an operating voltage of up to 500 V, therefore crane mechanisms are supplied with electrical equipment for voltages of 220, 380, 500 V AC and 220, 440 V DC. The control circuit provides maximum protection that turns off the motor in case of overload and short circuit. Zero protection prevents self-starting of motors when voltage is applied after a power outage. For safe maintenance of electrical equipment located on the bridge truss, blocking contacts are installed on the hatch and cabin door. When the hatch or door is opened, the voltage from the electrical equipment is removed.

The rules of Gosgortekhnadzor provide for four operating modes of mechanisms: light - L, medium - S, heavy - T, very heavy - VT.

The designed overhead crane operates in medium mode with duty cycle = 40%.

2.1 Kinematic diagrams of the main mechanisms

The operation of the main mechanisms of the crane is considered according to kinematic diagrams. Since engines usually have an angular velocity significantly greater than the speed of the lifting drum or the running wheels of a bridge or trolley, the movement to the working parts of the crane mechanisms is transmitted through gearboxes (indicated by the letter P in the figures).

For lifting mechanisms, the most widely used schemes are those with pulley block P (Figure 2), with the help of which the movement from drum B is transmitted to hook K.

Figure 3 shows a diagram of the trolley mechanism, which usually has four running wheels, two of which, connected by a shaft, are driven through a gearbox P from a motor D.

The transmission of motion to the running wheels of the end beams from the engine installed on the bridge can be carried out through the gearbox P, located in the middle part of the bridge (Figure 4).

Each crane mechanism has a mechanical brake T, which is installed on the coupling between the motor and the gearbox or on the brake pulley at the opposite end of the motor shaft.

Figure 2. Kinematic diagram of the lifting mechanism

Figure 3. Kinematic diagram of the trolley

Figure 4. Kinematic diagram of the bridge

REQUIREMENTS FOR THE ELECTRIC DRIVE SYSTEM AND RATIONALE FOR THE CHOSEN TYPE OF ELECTRIC DRIVE.

To select an electric drive system, it is necessary to clearly understand the technological requirements for the drive of the mechanism for which it is selected.

For high-quality lifting, lowering and moving of cargo, the electric drive of crane mechanisms must satisfy the following basic requirements:

1 Regulation of the angular speed of the engine within a relatively wide range due to the fact that it is advisable to move heavy loads at a lower speed, and an empty hook or an unloaded trolley at a higher speed to increase the productivity of the crane. Reduced speeds are also necessary for the precise stopping of transported goods in order to limit shocks during their landing and facilitate the operator’s work. Ensuring the necessary rigidity of the mechanical characteristics of the drive, especially the adjustment ones, so that low speeds are almost independent of the load.

3 Limitation of accelerations to acceptable limits with a minimum duration of transient processes. The first condition is associated with the weakening of shocks in mechanical transmissions when choosing a gap, with the prevention of slipping of the running wheels of trolleys and bridges, with a reduction in the swaying of a load suspended on ropes during intense acceleration and sharp braking of travel mechanisms; the second condition is necessary to ensure high performance of the crane.

4 Reversing the electric drive and ensuring its operation, both in motor mode and in braking mode.

4 OPERATING MODES OF CRANE ENGINES

Electric motors installed on cranes operate in harsh conditions, often in rooms with elevated temperatures or with a high content of vapors and gases, as well as in the open air. Bridge cranes have an intermittent operation mode, with frequent starts and braking.

Repeatedly - short-term mode is an engine operating mode in which operating periods t slave alternate with shutdown periods t 0.

Repeatedly - short-term operating mode is characterized by a relative ON duration (DS).

where, t slave – operating time (s)

t c – cycle time (s)

The nominal value of the relative switching duration is 15, 25, 40, 60%.

Let's consider the operating modes of the engines, which are presented in Figure 5.

The engines of the bridge and bogie mechanisms operate in normal motor mode when working with or without a load.

When lifting a load or an empty hook, the motor of the lifting mechanism operates in motor mode, and when lowering the load, two cases are possible:

If the moment of the load M gr is greater than the engine moment M dv, then the load will lower under the influence of its own weight taking into account the friction moment M tr and the electric motor must be turned on for lifting in order to slow down the load, that is, in this case the engine torque is equal to

M dv = M gr - M tr

This mode is called brake release.

If the moment of the load is less than the friction moment, then the electric motor must be turned on for descent and help lower the load, that is, work in motor mode, in this case the engine torque is equal to

dv = M tr - M gr

This mode is called power descent.

P

Power descent of small loads (motor mode)

Movement (motor mode)

Lifting a load (motor mode)

Brake release of load

Figure 5. Crane motor operating modes

When lowering an empty hook, two cases are also possible, that is, the descent can be both braking and power.

5 CALCULATION OF THE POWER OF ELECTRIC MOTORS, THEIR SELECTION BY CATEGORIES AND CHECKING.

5.1 Bridge engine.

We determine the resistance to movement of the mechanism when moving with a full load using formula 1

(1)

where, F Г – resistance to movement of the mechanism when moving with a full load, N;

G Г – weight of the crane with load, N;

G 0 – crane weight without load, N;

r – radius of the wheel axle, m;

We accept:

f = (0.0005-0.001).

µ = (0.015-0.02);

Calculate the weight of the crane with load

G G = m G g 10 3 (2)

where m Г is the crane’s lifting capacity, t;

G G = 10 9.8 10 3 =98000 N

Calculate the weight of the crane without load

G 0 = m 0 g 10 3 (3)

where m 0 is the weight of the bridge, i.e.

G 0 = 12 9.8 10 3 = 117600 N

Calculate the radius of the running wheel

R= (4)

where D x is the diameter of the bridge running wheels, m.

R=
m

Calculate the radius of the wheel axle

r =
(5)

where D c is the diameter of the bridge wheel axle, m.

r =
m

We calculate the resistance to movement of the mechanism using formula 1

We determine the resistance to movement of the mechanism when moving without load using formula 6

(6)

where, – F 0 resistance to movement of the mechanism when moving without load, N;

K – coefficient of friction of wheel ribs on rails;

G 0 – crane weight without load, N;

R – radius of the running wheel, m;

µ - coefficient of sliding friction in the bearing;

r – radius of the wheel axle, m;

f – rolling friction coefficient of the running wheel;

We accept:

µ = (0.015-0.02);

f = (0.0005-0.001).

We calculate F 0 using the formula:

We calculate the moment of static resistance on the electric motor shaft when moving with a load using formula 7

(7)

where, М с1 – moment of static resistance on the electric motor shaft when moving with a load, N m;

G – resistance to movement of the mechanism when moving with a full load, N;

n – engine rotation speed, rpm;

Finding the engine speed using formula 8

D x – diameter of the running wheel, m.

rpm

Nm

We calculate the load factor of the crane at idle using formula 9

(9)

G Г – weight of the crane with load, N;

G 0 – crane weight without load, N.

We calculate the moment of static resistance on the shaft without load using formula 10

(10)

where M s2 is the moment of static resistance on the motor shaft at

movement without load, Nm;

F 0 – resistance to movement of the mechanism when moving without load, N;

V – bridge movement speed, m/s;

n – engine speed, rpm

- Efficiency of the mechanism without load.

We calculate the efficiency of the mechanism without load using formula 11

(11)

where, Кз – load factor of the crane at idle;

Efficiency of the mechanism at full load.

We calculate the average static equivalent moment using formula 12

(12)

where, M e – average statistical moment, N m;

М с1 – moment of static resistance on the electric motor shaft when moving with a load, Nm;

M s2 – moment of static resistance on the engine shaft when moving without load, Nm.

Nm

Find the average equivalent power of the mechanism using formula 13

(13)

where, Р e – average equivalent power of the mechanism, kW;

M e – average statistical moment, N m;

n – engine rotation speed, rpm.

kW

We calculate the cycle time using formula 14

(14)

where t c – cycle time, s;

Z – number of cycles per hour

3600 – 1 hour, s;

With

We calculate the operating time when moving with and without a load using formula 15

(15)

where, t slave – operating time when moving with and without a load, s;

L – movement path of the mechanism, m;

V – bridge movement speed, m/s.

With

We calculate the duration of activation of the mechanism during operation using formula 16

(16)

Where,

t slave – operating time when moving with and without a load, s;

t c – cycle time, s.

We bring PV r to the standard value PV st = 30%

We calculate engine power using formula 17

where, PPVst – bridge engine power, kW;

Р e – average equivalent power of the mechanism, kW;

PV p – duration of activation of the mechanism during operation, %;

2.63 kW

According to the calculated rotation speed, taking into account the type of current according to the value of R PVst, we select a DC motor D31, the data of which is given in Table 1.

table 1

Let's determine the nominal torque using formula 18

M n =9.55·Рн/n (18)

M n =9.55·8000/820=93.1 N·m;

Let's determine the average starting torque of the engine using formula 19

M p =1.6-1.8M N (19)

where, M n =93.1 N m;

M p =1.6·93.1=148.96 N·m;

2. Let's determine the flywheel moment reduced to the motor shaft when the bridge moves with and without a load

With weight according to formula 20

SD gr ²=1.15 SD dv ²+365(G g + G 0)V²/n² N m (20)

Iа=0.3 kg m²

SD dv²=0.3·40=12 kg·m²

SD gr²=1.15 12+365(98000+117600) 1.25²/820²=196.3 N m²

Without load according to formula 21

We calculate the start time for each operation

The maximum permissible start time for travel mechanisms is 10-15 seconds

With formula 22 load

t p1= SD gr ² n/375 (Mn-Mst1) sec (22)

t p1= 196.3·820/375· (148.96-113.4)=12 sec

Without load according to formula 23

t p2= SD gr ² n/375 (Mn-Mst2) sec (23)

t p2= 113.5·820/375(148.96-67.5)=3 sec

because it turned out to be a short time to start the motor for moving the bridge without a load

t p2= 3 sec we calculate the engine of lower power

Let's check the DC motor D 22

Let's determine the nominal torque using formula 18

М n =9.55 Рн/n (18)

M n =9.55 6000/1070=53.5

We determine the average starting torque of the engine using formula 19

M p =1.8 M n (19)

M p =1.8 53.5=96.3

2. Let us determine the flywheel moment reduced to the motor shaft when the bridge moves with a load according to formula 20

I i = 0.155 kg m²

SD dv ²=0.155 40 =6.2 kg m²

SD gr ²=1.15 6.2+365(98000+117600)1.25 ² /1070²=114.52 N m²

3.without load according to formula 21

SD 0 ²=1.15 6.2+365(117600 1.25 ²)/1070 ²=65.7 N m²

4. We calculate the start time for each operation with the load using formula 22

t p1= (114.52 1070)/375(96.3-113.4)=-19.1 sec

since the result is a negative value, the start time of the bridge movement motor t p1 = -19.1, then the D 22 motor is not suitable

For the D 31 engine, when calculating the starting time without a load, we will reduce the starting torque by introducing a rheostat into the circuit according to formula 22

M p =1 M n =1 93.1=93.1 N m (22)

5.Calculate the launch time without load using formula 23

t p2 =113.5 820/375(93.1-67.5)=9.6 sec

6.Calculate the braking time for each operation with a load using formula 24

t t = SD gr ² n/375(M t + M st) sec (24)

M t = M n =93.1 N m

t t1 =196.3 820/375(93.1+113.4)=2 sec

7. To calculate the braking time without a load, we limit the braking torque using formula 24

M t =0.8 M nom =0.8 93.1=74.48 N m (25)

t t2= 113.5 820/375(74.48+67.5)=1.74 sec

8. We find the deceleration using formula 26

a=v/ t n ≤0.6;0.8 (26)

without load

1=0.6≤0.6;0.8 a2=0.7≤0.6;0.8

9. Let us determine the time of steady motion tус according to formula 27

t y =360 · 0.106-12-9.6-2-1.74/2=6.4 sec

10. Constructing a load diagram

11.Calculate the equivalent moment using formula 28

(28)

2. Let us determine the equivalent moment recalculated to standard PV using formula 29

(29)

=48.6 Nm

48.6≤93.1 - conditions are met, the engine is checked according to the maximum permissible overload

0.8λcr·Mon≤Mst.max

0.8 3 93.1≤113.4

The conditions are met, therefore, to move the bridge we use a DC motor D 31

5.2 Trolley engines

1. Determine the resistance to movement of the mechanism when moving with a full load using formula 1

We determine the weight of the crane G G with a load using formula 2

G G = 10 9.8 10 3 = 98000 N

We determine the weight of the crane without load G 0 using formula 3

G 0 = m 0 g 10 3 (3)

where m 0 is the weight of the trolley, i.e.

G 0 = 5.6 9.8 10 3 = 54880 N

Find the radius of the running wheel using formula 4

where, D x – diameter of the trolley running wheels, m.

Find the radius of the wheel axle using formula 5

where, D c – diameter of the trolley wheel axle, m.

r =
m

Find the resistance to movement of the mechanism when moving with a full load using formula 1

2. Determine the resistance to movement of the mechanism when moving without a load using formula 6

3. We calculate the moment of static resistance on the electric motor shaft when moving with a load using formula 7

rpm

Nm

4. We calculate the load factor of the crane at idle using formula 9

(9)

=0,35

5. Let's determine the efficiency x.x using formula 11

6. We calculate the moment of static resistance on the shaft without load using formula 10

Nm

7. Calculate the average static equivalent moment using formula 12

Nm

8. Find the average equivalent power of the mechanism using formula 13

kW

9. Calculate the cycle time using formula 14

(14)

With

0. We calculate the operating time when moving with and without a load using formula 15

(15)

With

11. Calculate the duration of activation of the mechanism during operation using formula 16

(16)

We bring PV r to the standard value PV st = 25%

12. Calculate the power of the mechanism using formula 17

kW

Based on the obtained power of the mechanism and the calculated rotation speed, taking into account the type of current, a DC motor of brand D 12 is selected, the data of which is given in Table 2.

table 2

We check the selected engine.

The engine is tested under two conditions;

1. Determine the average starting torque using formula 18

M start = (1.6-1.8) M nom (18)

where M nom is the rated torque of the engine, Nm is determined by formula 19

(19)

Nm

M start = 1.6 20.9 = 33.44 Nm

2. We calculate the flywheel moment reduced to the motor shaft

with cargo according to formula 20

I i =0.05 kg m 2

SD dv ²=0.05 40=2

SD gr ²=1.15 SD dv ²+365(Cg+C0) V/n² N m² (20)

SD gr²=1.15 2+365(98000+54880) 0.6²/1140²=17.7 N m²

Without load according to formula 21

SD 0 ²=1.15 SD dv ²+365(C 0 V²)/n² N m² (21)

SD 0 ²=1.15 2+365(54880 0.6²)/1140²=7.8 N m²

3. Now we calculate the start time for each operation

With formula 22 load

With

4. Calculate braking time

t = M nom = 20.9 N m

With formula 24 load

With

Without load according to formula 24

5. Deceleration according to formula 26

a=V/tt≤0.6-0.8 (26)

a1 =0.6/1.3=0.46

without load

a2=0.6/0.83=0.72

a1=0.46≤0.6-0.8

a2=0.72≤0.6-0.8

6. Calculate the steady-state time of movement of the mechanism using formula 27

Building a load diagram

8. Determine the equivalent engine torque using formula 28

9. Calculate the equivalent moment using formula 29

=7.1 N m

7.1≤20.9 – the condition is met, the engine is checked according to the maximum permissible overload

0.8λcr·Mon≤Mst.max

0.8·3·20.9≤17.8

The engine has a low load, because there are no engines of lower power

5.3 Hoist motors

1. Determine the moment of static resistance on the motor shaft when lifting a load using formula 30

Where,

G Г – weight of the crane with load, N;

G 0 – weight of the crane (load-handling device) without load, N;

Efficiency of the lift when lifting loads;

i рп – gear ratio of the gearbox, taking into account the multiplicity of pulleys.

g – free fall acceleration, m/s.

Find the weight of the crane (load-handling device) without load using formula 3

G 0 = m 0 g 10 3 (3)

where m 0 is the weight of the lifting device, i.e.

G 0 = 1.2 9.8 10 3 =11760 N

i rp = i r · i p =34.2 · 2=68.4

where, i р – gear reduction ratio of the drive;

i p – multiplicity of pulleys.

Nm

2. Determine the moment of static resistance on the motor shaft when lowering the load (brake release) using formula 31

M s2 = M s1 ·(2·-1) (31)

where, М с2 – moment of static resistance on the motor shaft when lowering the load, N m;

М с1 – moment of static resistance on the electric motor shaft when lifting a load, Nm;

Efficiency of the lift.

M s2 = 457·(0.79·2-1) = 265 N·m

3. Determine the moment of static resistance on the motor shaft when lifting the load-handling device using formula 32

(32)

where, M с3 is the moment of static resistance on the motor shaft when lifting the load-handling device without a load, N m;

G 0 – weight of the load-handling device without load, N;

D b – diameter of the lifting winch drum, m;

i рп – gear ratio of the gearbox, taking into account the multiplicity of pulleys;

4. Find the efficiency of the lift when lifting and lowering the load-handling device without a load using formula 11

(11)

5. We calculate the load factor of the crane at idle using formula 9

6. Determine the moment of static resistance on the motor shaft when lowering the load-gripping device without a load according to formula 31

М с4 = М с3 ·(2·-1) (31)

where, M c4 is the moment of static resistance on the motor shaft when lowering the load-grabbing device without a load, N m;

M s3 - moment of static resistance on the motor shaft during lifting

load-handling device without load, Nm;

Efficiency of the lift when lifting and lowering the load-handling device without a load.

M s4 = 265·(2·0.38-1) = -63.6 Nm

7. Calculate the equivalent static moment with a prime using formula 33

(33)

where, M e ’ - equivalent moment with a prime, N m;

М с1 – moment of static resistance on the electric motor shaft when lifting a load, Nm;

М с2 – moment of static resistance on the motor shaft when lowering the load, Nm;

M s3 - moment of static resistance on the motor shaft when lifting the load-handling device without a load, Nm;

M с4 is the moment of static resistance on the motor shaft when lowering the load-handling device without a load, Nm.

8. Calculate the cycle time using formula 14

(14)

With

9. We calculate the operating time when moving with and without a load using formula 15

(15)

where L – lifting height, m.

With

10. Calculate the duration of activation of the mechanism during operation

We bring PV r to the standard value PV st = 40%

11. Determine the equivalent static moment using formula 28

(28)

where, M e - equivalent static moment, N m;

M e ’ - equivalent moment with a prime, N m;

PV p – duration of activation of the mechanism during operation, %;

PV st – standard duration of switching on, %.

Nm

12. Find the engine speed using formula 8

(8)

where, i рп – gear reduction ratio of the drive, taking into account the multiplicity of pulleys;

D b – drum diameter, m.

rpm

13. Find the average equivalent power of the mechanism using formula 13

kW

Based on the received power of the mechanism, the DC motor D806 is selected

We check the selected engine.

Table 3

We calculate and construct a load diagram

The pre-selected motor is checked for heating conditions, a load diagram is constructed taking into account starting and braking modes

1. Determine the average starting torque using formula 19

M start – average value of the engine starting torque, Nm;

M start = (1.6-1.8) M nom (19)

where M nom is the rated torque of the engine, Nm is determined by formula 18

where, P nom – rated power of the selected engine, kW;

n nom – rated rotation speed of the selected engine, rpm.

M start = 1.5 330 = 495 Nm

2. We calculate the flywheel torque reduced to the motor shaft using formula 20

SD dv ²=1·40=40 kg·m²

SD gr ²=1.15 SD dv ²+365(Cg+C0) V/n² N m² (20)

SD gr²=1.15·40+365(9800+11760) ·0.2²/635²=53.3 N m²

Without load according to formula 21

SD 0 ²=1.15 SD dv ²+365(С 0 ·V²)/n² N m² (21)

SD 0 ²=1.15·40+365(11760·0.2²)/635²=46.42 N m²

3. Now we calculate the start time for each operation using formula 22

With

With

Without load

With

4. Calculate braking time using formula 24

t = M nom =330 Nm

t t1,t t2 – braking time with and without load, s.

With

Without load

With

5. Deceleration according to formula 25

a=V/tt≤0.6-0.8 (25)

a1 =0.2/0.1=2 a2=0.2/0.15=1.33

without load

a3=0.2/0.18=1.11 a4=0.2/0.29=0.68

6. Let us determine the time of steady motion tус according to formula 26 (26)

7. Calculate the equivalent moment using formula 27

8. Calculate the equivalent moment using formula 28

=288.33 Nm

288.33≤330 – the condition is met, the engine satisfies the heating conditions

9. Check for overload using formula 34

Λ cr =Mmax/Mn=981/330=2.9 (34)

0.8λcr·Mon≤Mst.max

0.8 2.9 330≥457

The condition is met, we take the D806 engine with a power of 22 kW as the drive of the lifting mechanism

CALCULATION AND CONSTRUCTION OF MECHANICAL CHARACTERISTICS OF ENGINES.

A mechanical characteristic is the dependence of engine rotation speed on torque.

The engine performance will be natural under the following conditions:

The stator voltage must be rated;

If there are no additional resistances in the stator and rotor;

On alternating current, the frequency will be exactly 50 Hz;

In order to construct a natural characteristic, it is necessary to calculate three points for the mechanisms.

6.1 For the bridge motor, we determine the point x.x M=I=0

Point 1 has coordinates

where, n 0 – engine speed at start-up, rpm.

We calculate T1 - at ideal idle

Find the engine speed when starting using formula 35

n 0 =Un/nn ·Un-In ·Rdv rpm

where, n 0 – engine speed at start-up, rpm;

Rdv =0.5 · Un(1- nn)/ In=0.5 ·220(1-0.84)/44=0.4 Ohm

n 0 =820 ·220/220-44 ·0.4=885.6 rpm

Point 2 has coordinates

T2 (M nom; n nom)

n rated – rated engine speed, rpm.

М=Мн=9.55 Рн/ n nom=9.55 8000/820=93.1 Nm

We calculate T2 - in working or nominal T2 (93.1; 820)

Mechanical characteristics of the bridge motor

2 For trolley motor

Point 1 has coordinates

(36)

Rdv =0.5 · Un(1- nn)/ In=0.5 ·220(1-0.85)/14.6=1.13 Ohm

n 0 =1140 ·220/220-14.6 ·1.13=1231.2 rpm

Point 2 has coordinates

T2 (M nom; n nom)

where, M nom – rated torque of the engine, Nm; find by formula 18

М=Мн=9.55 Рн/ n nom =9.55 2500/1140=20.9 N m

T2 (20.9; 1140)

Mechanical characteristics of the trolley engine

3 For hoist motor

Point 1 has coordinates

Find the engine speed when starting using formula 36

Rdv =0.5 · Un(1- nn)/ In=0.5 ·220(1-0.79)/116=0.19 Ohm

n 0 =635 ·220/220-116 ·0.19=704.85 rpm

Point 2 has coordinates

T2 (M nom; n nom)

where, M nom – rated torque of the engine, Nm; find by formula 18

n nom – rated engine speed, rpm.

М=Мн=9.55 Рн/ n nom =9.55 22000/635=330 N m

Mechanical characteristics of the lifting mechanism motor

CALCULATION AND SELECTION OF STARTING, BRAKE AND ADJUSTMENT RESISTANCES.

A starting resistance (rheostat) is a device that serves to introduce and remove resistance in the rotor circuit during the startup and acceleration of the electric drive.

The introduction and removal of resistance is carried out in stages (in sections).

To calculate starting resistances, the number of steps Z is specified

Z=1-2 for motors up to 10 kW

Z=2-3 for motors up to 50 kW

Analytical method

7.1. We carry out calculations for the bridge

1. For bridge Z=2

M=Mst1/Mn=113.4/93.1=1.21 (37)

Ist.max = I · In = 1.21 · 44 = 53.24 A (38)

I 2 =(1.1-1.2) Ist.max=1.2 53.24=63.88 A (39)

(40)

Where, - ratio of I 1 to I 2;

(42)

Ohm

(43)

Where,

The ratio of I 1 to I 2.

Ohm

(44)

R 2 - resistance at the second stage, Ohm;

The ratio of I 1 to I 2.

Ohm

9. Find the calculated moment using formula 45

M 1 =I 1 /In ·Mn=130.3/44 ·93.1=275.7 N ·m

M 2 =I 2 /In ·Mn=63.88/44 ·93.1=135.1 N ·m

r 1 = R 1 – R 2 (46)

r 2 = R 2 – R 3

r 1 = 1.68 – 0.82 = 0.86 Ohm

r 2 = 0.82 – 0.4 = 0.42 Ohm

R p = r 1 - r dv (47)

R p = 1.68-0.4 = 1.28 Ohm

RUн/Iн=220/44=5 Ohm

R1=a1/a=30/90=0.33 R1=R1 Rn=0.33 5=1.65

R2=av/ad=15/90=0.16 R2=R2 Rn=0.16 5=0.8

Rn=Un/In=220/44=5 Rdv= Rdv ·Rn=0.08 ·5=0.4

Rdv=ab/ad=8/90=0.08

All calculations were made correctly

7.2. For trolley

1. For trolley Z=2

We determine the torque on the engine using formula 37

M=Mst1/Mn=17.8/20.9=0.85 (37)

2. Calculate the maximum static current using formula 38

Ist.max = I · In = 0.85 · 14.6 = 12.41 A (38)

3. We calculate the current when calculating the starting resistance using formula 39

I 2 =(1.1-1.2) Ist.max=1.2 12.41=14.89 A (39)

4. Determine the design current when calculating the starting resistance using formula 40

5. Find the ratio of I 1 to I 2 using formula 41

where, is the ratio of I 1 to I 2;

I 1 - calculated current when calculating starting resistance, A;

I 2 - current when calculating starting resistance, A.

6. Calculate the resistance at the first stage using formula 42

where, R 1 - resistance at the first stage, Ohm;

U 2 – rated voltage between the rotor rings, V;

I 1 - calculated current when calculating starting resistance, A.

Ohm

7. Calculate the resistance at the second stage using formula 43

R 1 - resistance at the first stage, Ohm;

The ratio of I 1 to I 2.

Ohm

8. Calculate the motor resistance using formula 44

where, R dv - resistance at the third stage, Ohm;

R 2 - resistance at the second stage, Ohm;

The ratio of I 1 to I 2.

Ohm

M 1 =I 1 /In ·Mn=34.9/14.6 ·20.9=50 N m (45)

M 2 =I 2 /In ·Mn=14.89/14.6 ·20.9=21.3 N ·m

10. Find the resistance of the starting rheostat sections using formula 46

r 1 = R 1 – R 2 (46)

r 2 = R 2 – R 3

where, r 1, r 2, resistances of the first, second and third sections, Ohm;

R 1 , R 2 , R 3 – resistance of the first, second and third stages, Ohm;

R motor – motor resistance, Ohm.

r 1 = 6.3 - 2.7 = 3.6 Ohm

2 = 2.7 – 1.17 = 1.53 Ohm

11. Find the total starting resistance of the rheostat using formula 47

R p = r 1 - r dv (47)

R p = 6.3-1.17 = 5.13 Ohm

R n = Un/In = 220/14.6 = 15 Ohm

12. Let's calculate the starting resistance for the bridge mechanism graphically

R1=a1/a=50/121=0.41 R1=R1 Rn=0.41 15=6.15

R2=av/ad=21/121=0.17 R2=R2 Rn=0.17 15=2.55

Rn=Un/In=220/14.6=15 Rdv= Rdv ·Rn=0.07 ·15=1.05

Rdv=ab/ad=9/121=0.07

All calculations were made correctly

7.3 For lifting mechanism

1. For bridge Z=3

We determine the torque on the engine using formula 37

M=Mst1/Mn=457/330=1.38 (37)

2. Calculate the maximum static current using formula 38

Ist.max= I In=1.38 116=160 A (38)

3. We calculate the current when calculating the starting resistance using formula 39

I 2 =(1.1-1.2) Ist.max=1.2 160=192 A (39)

We determine the design current when calculating the starting resistance using formula 40

5. Find the ratio of I 1 to I 2 using formula 41

where, is the ratio of I 1 to I 2;

I 1 - calculated current when calculating starting resistance, A;

I 2 - current when calculating starting resistance, A.

6. Calculate the resistance at the first stage using formula 42

where, R 1 - resistance at the first stage, Ohm;

U 2 – rated voltage between the rotor rings, V;

I 1 - calculated current when calculating starting resistance, A.

Ohm

We calculate the resistance at the second stage using formula 43

where, R 2 - resistance at the second stage, Ohm;

R 1 - resistance at the first stage, Ohm;

The ratio of I 1 to I 2.

Ohm

8. Calculate the motor resistance using formula 44

(44)

where, R dv - resistance at the third stage, Ohm;

R 2 - resistance at the second stage, Ohm;

The ratio of I 1 to I 2.

Ohm

Finding the total resistance using formula 48

Rп=R1-Rдв=0.73-0.18=0.550 Ohm (48)

9. Find the calculated moment using formula 45

M 1 =I 1 /In ·Mn=299.52/116 ·330=852 N ·m

M 2 =I 2 /In ·Mn=192/116 ·330=546.2 N ·m

10. Find the resistance of the starting rheostat sections using formula 46

r 1 = R 1 – R 2

r 2 = R 2 – R 3

where, r 1, r 2, r 3 resistances of the first, second and third sections, Ohm;

R 1 , R 2 , R 3 – resistance of the first, second and third stages, Ohm;

R motor – motor resistance, Ohm.

r 1 = 0.73 – 0.46 = 0.27 Ohm

r 2 = 0.46 – 0.29 = 0.17 Ohm

r 3 =0.29-0.18=0.11

R n = Un/In = 220/116 = 1.89 Ohm

11. Let's calculate the starting resistance for the bridge mechanism graphically

R1=a1/a=27/71=0.38 R1=R1 Rn=0.38 1.89=0.71

R2=av/ad=17/21=0.23 R2=R2 Rn=0.23 1.89=0.43

R3=av/ad=11/71=0.15 R3=R3 Rn=0.15 1.89=0.28

Rn=Un/In=220/116=1.89 Rdv= Rdv ·Rn=0.09 ·1.89=0.17

Rdv=ab/ad=7/71=0.09

all calculations were made correctly

Control Scheme Selection

A schematic diagram is an expanded diagram of electrical connections. It is the main diagram of the project

electrical equipment of an overhead crane and gives a general idea of ​​the electrical equipment of this mechanism, reflects the operation of the automatic control system of the mechanism. The diagram is used to check the correctness of electrical connections during installation and commissioning of electrical equipment.

The control circuit of the overhead crane includes a protective panel PPZK, an electric drive circuit for the bridge moving mechanism, and an electric drive circuit for the trolley moving and lifting mechanism.

9. SELECTION OF CONTROL AND PROTECTION EQUIPMENT.

9.1 Controllers

Controllers are power (cam) and magnetic (command controllers).

Power controllers are connected with their contacts to the power circuits of the motors.

Magnetic controllers with their contacts are included in the control circuit and through these contacts in certain positions they receive power to the contactor coils, which with their contacts will supply power to the motor.

1. Selecting a controller for axle and trolley

When choosing a controller you need to consider;

Engine power;

Stator current;

Type of current;

Rated voltage;

Estimated duration of switching on.

Axle and bogie motor data

Alternating current

R n m = 8 kW

R n t = 2.5 kW

According to the reference book Yaure A.G. “Crane electric drive”, select power cam controllers

slave. positive 6/6

voltage 220V

engine power 10kW

2. Selecting a controller for the lifting mechanism

We choose a magnetic DC controller type PS or DPS, designed to control electric drives of lifting mechanisms

For a lifting mechanism with Rn = 22 kW, use the reference book to select a PS type controller

Switching current 450A

Voltage 220V

Power used motor 30kW

Crane limit switches

Limit switches

Crane limit switches are used to prevent the mechanisms from passing maximum permissible positions (limiting the lifting of the load gripping device or the travel of the bridge and trolley), as well as blocking the opening of hatches and cabin doors.

1. Limit switches are selected taking into account the speed of movement of the mechanisms.

Let's select limit switches

For moving mechanisms - KU 701 lever with self-return

For lifting - KU 703 with self-return from the load

Mechanism speed 0.03-2 m/s

Protection degree IP44

Weight 2.7 kg

Mechanism speed 0.01-1 m/s

Protection degree IP44

Weight 10.3 kg

9.3 Maximum relays type RE0401 for protection of crane circuits

1. Calculation of the maximum relay using formula 48

Isr=2.5·In (48)

For the bridge Iср=2.5·44=110 А

For a trolley Iср=2.5·14.6=36.5 А

For lifting Iср=2.5·116=290 А

For group Imax =241.2

Iav=2.5·241.2=603 A

For moving and lifting mechanisms, we select relays of type RE0401

RelayRE0401	Electromagnet	Coil current	Current regulation limits	Coil terminals
1.bridge TD.304.096-12
2. Trolley 2TD.304.096-18
3.Lift 2TD.304.096-8
4. group 2TD.304.096-4

9.4 Resistors

Used for starting, angular velocity control and braking

Resistors are selected according to the total value of the starting resistance, taking into account the values ​​of the sections

1. We select resistors:

For bridge Rn=220/44=5 Ohm

For trolley Rn=220/14.6=15 Ohm

For lifting Rn=220/116=1.89 Ohm

Controller KV101

Nominal resistance Rn=5 Ohm

Engine power Рн=8kW

Block type BK12

Block ruble 02

Number of blocks 1

2. Trolley

Controller KV101 Nominal resistance Rn=15 Ohm

Engine power Рн=2.5 kW

Block type BK12

Block ruble 03

Number of blocks 1

Controller PS 160

Nominal resistance Rn=1.89 Ohm

Engine power Рн=22kW

Block type BK6

Block ruble 07

Number of blocks 1

9.5 Protective panel

The crane protective panel provides the following types of protection:

Power supply is carried out using zero contacts and a contactor.

Protection against short circuit currents and large overloads over 250%.

Limit protection, which provides deviations when the crane mechanisms reach extreme positions, is carried out using limit switches.

Blocking prevents engines from starting when the cabin door is open and the hatch is open.

Emergency shutdown.

Shutdown when the network voltage drops by more than 15%.

9.6 Fuses

For crane protective panels with I max = 6A, fuses are selected according to the condition I st ≥ I max

According to I max, fuses of type PR-2-15 are selected, I inst = 6A

The design of the protective panel is a metal cabinet with equipment installed in it

The protective panel is placed in the crane cabin

Selecting a PPZK type protective panel for three DC motors

Main equipment of PPZK

Input switch QW

Linear contactor KM

Fuses FU

Sunroof and door contact SQ

Limit switch contacts SQ

Emergency switchA

Selecting the protective panel PPZB 160

10. CURRENT LINE TO THE CRANE MOTORS, SELECTION OF TROLLEYS AND CHECKING THEM FOR PERMISSIBLE VOLTAGE LOSS .

The current supply to the crane motors is carried out from the general network of the workshop substation.

Since the crane mechanisms move along with the engines and equipment, the current supply to them is carried out using trolley contact wires or flexible copper cables.

From the workshop transformer substation, through a linear circuit breaker, a cable supplies power to the main assembly, and from it power is supplied to the main trolleys, which are installed on insulators along the crane runway, at a safe height on the side opposite the cabin.

Current collection is carried out as follows: cast iron shoes, which are attached to insulators, slide along the edges of the trolley corners, made of profiled steel. Current collection lightning bolts are connected to the bridge.

Using copper multi-pin jumpers, the shoes are connected by clamps to the linear box located on the bridge, and from them wires and cables go to the protective panel.

The trolleys are located along the bridge span, and the current collector is located on a trolley.

The selection of trolley sections is carried out based on continuous current and is checked for permissible voltage loss.

For trolleys, profiled steel with profile 5, 6, 7.5 is used:

5×40×40; 6×63×63; 7.5×80×80.

10.1. Main trolls

1. Determine the load of the crane using formula 49

Рр=Кн ·Р∑+С ·Р3 (49)

Р∑-sum of powers of all engines =Р3

Kn – utilization factor = 0.12

Рр=0.12 ·32.5+0.3 ·32.5=13650W

2. The design current is determined by formula 50

Ip=Pp/Un ·ηav=13650/220 ·0.82=75.6 A (50)

ηav = ηm+ ηt+ ηp/3=0.84+0.85+0.79/3=0.82

3. Trolley size 50 · 50 · 5 mm

R0=0.27Ohm/0.001=0.00027Ohm

4. Check for voltage loss using formula 51

U=200 ·Imax ·lR0/Un≤3-4% (51)

In this case: Imax=K In1+ In2=1.7 116+44=241.2 A

We accept:

U=200 ·241.2 ·240.00027/220=1.42%≤3-4%

From the trolley calculations we select 50 · 50 · 5 mm

Wiring is carried out using PRTO-500 wire

Ip= In=44 A S=10mm²

2. Trolley

Ip= In=14.6 A S=2.5mm²

Ip= In=116 A S=50mm²

p=1.7 116+14.6+44=255.8 A S=150mm²

11 CALCULATION AND SELECTION OF BRAKES.

The crane mechanism must have a device to stop it in this position or limit the braking distance when escaping after the drive motor is turned off. Such devices are called brakes, which stop the crane mechanism due to frictional forces between a rotating pulley or disk and a stationary braking surface associated with the mechanism.

11.1 Calculation of brakes for the bridge

1. Determine the calculation of the braking force required to stop the mechanism using formula 52

Mtr - braking torque, Nm.

Torque torque 125

11.2. For trolley mechanism

where, PV p – design duration of switching on, %;

PV st – standard switching duration, %;

Mtr - braking torque, Nm.

Brake torque 16 N m

11.3. for the lifting mechanism according to formula 56

Mt≥Kz · M tr (56)

In this case: Kz=1.75

We determine the calculation of the braking torque required to stop the mechanism using formula 57

M tr. =94 ·Q ·V ·η/n=94 ·10000 ·0.2 ·0.79/635=233.8N·m (57)

Mt≥1.75 ·233.8

where, PV p – design duration of switching on, %;

PV st – standard switching duration, %;

Mtr - braking torque, Nm.

Choose brakes 420≤429.6

Brake torque 420 N m

12 DESCRIPTION OF THE CIRCUIT DIAGRAM OF THE CRANE ELECTRICAL EQUIPMENT

The overhead crane is driven by three motors. The bridge engine moves the bridge along the workshop rails. On the bridge, a trolley moves along rails, and there is a lifting mechanism on the trolley.

On all three mechanisms, parallel-excited DC motors are selected.

For the bridge mechanism, travel speed 1.25 m/s-D31, Rnom = 8 kW; for the trolley mechanism, travel speed 0.6 m/s-D 12, Rnom = 2.5 kW; for the lifting mechanism, travel speed 0.2 m/s –D806,Rnom=22 kW

Protection level IP44

The circuit diagram includes four arranged circuits. Diagram of the protective panel to which three motors are connected.

To control electric drives of an overhead crane, power cam controllers are used for movement mechanisms and a magnetic controller is used for the lifting mechanism. Resistors are used to limit the starting current, regulate the angular speed and brake the motors.

To prevent mechanisms from crossing maximum permissible positions, limit switches of the KU701 and KU703 series are used

To protect against current loads and short circuit currents, to ensure emergency shutdown, a protective panel of the PPZK type is used

The current conduction is carried out using contact wires - trolleys with dimensions of 50·50·5 mm

The mechanism uses DC electromagnets type MP101, MP301, MP201 with brakes TKP100, TKP200, TKP300

13 ISSUES OF OPERATION AND INSTALLATION OF ELECTRICAL EQUIPMENT OF THE CRANE

The equipment and electrical wiring of the crane cabin are installed in workshops. The cabin is then transported to the construction site, installed on the crane and connected to the crane's electrical circuitry. The industry produces ballasts, assembled in the form of resistance boxes, in open and protected versions. On the cranes they are located either in the control cabin or on the bridge, and in the switchboard rooms of control stations - at the top of the wall in such a way as to reduce the length of the connecting wires as much as possible and ensure the removal of heat generated by them during operation, without thereby worsening the operating conditions of the wires and other equipment. Resistance boxes are installed so that their elements are located “on edge”. No more than three resistance boxes can be mounted directly on top of each other. For larger quantities (no more than six), a metal frame in the form of a bookcase is made for them. When installing, make sure that the leads from the resistance elements are on one side of the resistance boxes. All connections between boxes are made with bare steel or copper wires and busbars. The busbar is made as short as possible.

Brake electromagnets are installed directly at the electric motor pulley (in the place provided for this purpose during the manufacture of the unit at the factory) and secured with bolts. When installing, ensure a strictly vertical position of the electromagnet and an equal gap between the brake pads and the drum along the entire length of the pads. Skew is not allowed. There should also be no jamming or distortion of the electromagnet armature, as they entail possible overheating and even burning of its winding. The armature is connected to the brake in such a way as to ensure a smooth descent and ascent of the brake pads.

Drawings sent by manufacturers usually indicate the location in the cab where the drum or cam controllers should be located.

To eliminate vibrations of controller parts and protect wires from breakage and loosening of contact connections, controllers should be firmly attached either to the floor or to structures. Installed controllers are checked by plumb and level. For ease of maintenance, the height of the controller steering wheel above the cabin floor level is no more than 1150 mm.

The limit switches for the movement of overhead cranes are placed on special structures on the sides of the transverse truss of the crane, and the switches for the movement of the trolley are located at the ends of its guides. Limit rails or switching stops relative to the trip lever of the limit switch must be fixed so that their axes coincide. The length of the limiting rail and the installation location of the trip stop are determined depending on the length of the braking path at the maximum speed of movement of the moving part of the mechanism. Electrical equipment for cranes is currently installed using the industrial method at manufacturing plants or workshops for electrical installation workpieces.

14 SAFETY ISSUES DURING MAINTENANCE AND INSTALLATION OF ELECTRICAL EQUIPMENT OF THE CRANE.

Personnel servicing the electrical equipment of lifting devices must be careful and strictly comply with all safety requirements (use proven, wired dielectric gloves and galoshes, insulating stands and mats, tools equipped with insulating handles).

Before starting to measure insulation resistance values, the part of the electrical installation being tested is turned off. The absence of voltage on disconnected parts of the electrical installation is checked with a voltage indicator.

Carrying out work on parts of lifting devices that are in motion poses a great danger. Operations that are strictly prohibited when operating lifting devices include securing equipment and devices, adjustment work, and cleaning collectors and slip rings.

Repair of electrical equipment of lifting devices according to safety conditions is carried out by two people, one of them is a manager who has the necessary experience and qualifications and is responsible for the safe organization of work. Without the permission of the responsible person, it is prohibited to supply power to the lifting device for checking and adjusting the mechanisms after completion of repair work. The permission of the responsible person is also required to put a repaired crane into operation.

Electric cranes are repaired in “repair pens” specially designed for this purpose. To ensure the safety of work, crane trolleys located within the “repair pens” are disconnected from the rest of the trolleys and grounded during repairs. Before starting repair work, check the position of the disconnect switch and the reliability of the grounding of the crane trolleys and in the “repair pens”.

Safety precautions when installing electrical equipment of lifting and transport devices. Features of the installation of crane installations (work at height in the presence of large masses of metal and the associated inconvenience of its implementation) require compliance with appropriate safety measures. All places where people can fall must be fenced. Entry to the crane is permitted only via a specially constructed staircase with railings. Tools, materials and equipment should only be lifted onto the crane using hemp rope.

The area under the mounted crane is fenced off and a poster is posted: “Passage is prohibited! They are working at the top.” Working with power tools is allowed only with rubber gloves and galoshes, and the tool must be grounded. Electricity is supplied to the power tool through a hose wire with good insulation. In places where you can fall, work in a safety belt. Electric welding wires must have reliable insulation, and the welder must work in rubber galoshes or boots.

List of sources used

1 E. N. Zimin, V. I. Preobrazhensky, I. I. Chuvashov, Electrical equipment of industrial enterprises and installations. – M.: Energoizdat, 1999.

2 Aliev V.P. Handbook of electrical engineering and electrical equipment (5th ed., revised) / Series “Reference Books”. - Rostov-on-Don: Phoenix, 1988.

3 A. G. Yaure, E. M. Pevzner. Electric crane drive: Directory - M.: Energoatomizdat, 1988.

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Figure 11.1 shows a diagram of the most common overhead crane in industry, consisting of the following components: control cabin 1 , crane movement mechanism2 , power supply cable for cargo trolley 3, electrical equipment 4 , crane bridge5 , cargo trolley 6 , installation of the main pantograph7 , cabins for trolley maintenance 8.

Figure 11.1

The crane bridge rests on running wheels and moves along crane tracks laid on the projections of the upper part of the workshop wall. The running wheels of the crane are driven into rotation by the crane's travel mechanisms, which consist of separate drives installed on the platforms of the bridge span.

Cart moves on two rails fixed to the main beams of the bridge. Electrical equipment is located on the bridge platforms, on the trolley and in the control cabin. The crane is powered through rigid corner trolleys located along the crane tracks.

The trolley mechanisms are powered through a flexible cable suspended on a special monorail track using movable carriages.

The operating mode of the lifting machine is cyclic. The cycle consists of moving the load along a given path and returning the machine to its original position for a new cycle. In the crane operation cycle, the switching time (operation) of any of its mechanisms alternates with the pause time of this mechanism (while another mechanism is switched on, the load is slinged or unslinged, or a technological pause occurs).

Currently, various control systems for electric drives of overhead cranes are used. One of the most advanced is the AC electric drive system with hour volt converters and control from the controller, the diagram of which is shown in Figure 11.1. Converters are used as frequency convertersMOVITRAC -31 С110-503-4-00 AndС370-503-4-00 companiesSEWErodrive , which are performed with an intermediate DC link and sinusoidal pulse-width modulation (PWM) of the inverter output voltage. The devices are connected directly to a three-phase alternating current network with a voltage from 3x380 to 3x500 V and a frequency of 50 (60) Hz. They provide a change in the three-phase output voltage to the value of the mains voltage with a proportionally increasing output frequency to an adjustable value of the base frequency, located in the range of 50...150 Hz (for special characteristics from 5 to 400 Hz). This feature allows you to control three-phase IM with a constant torque until the rated frequency is reached, and above it - with a constant power.

The operator's station is based on a keypadFBG 31С-01, which includes a backlit text display, three languages ​​to choose from and a membrane panel with six keys. The display shows an extended and short menu of parameters. The keypad provides: display of output frequency, current, temperature and other measured values; fixing faults; reading and correction of all parameters; saving data. To control the lifting and moving mechanisms, ergonomic joystick-type hand manipulators are used.

The control system for electric drives of an overhead crane is implemented on a controller with the ability to communicate with a PC via a serial RS-485 interface to exchange information with the upper control level and the remote control level.

11.2.2 Gantry crane control system

Gantry cranes are used mainly in the construction of buildings, loading and unloading ships in sea or river ports. Loading and unloading and other types of work are carried out by several electric drives of varying power. AC electric motors with control from a frequency converter are used as drives. Let's consider the control system for a gantry (gantry) full-rotating crane of the "Falcon" type.

The crane diagram is shown in Figure 11.2, where1 – mechanism for turning the cargo traverse; 2 – mechanism for changing the boom extension;3- engine room; 4,8 – turning mechanisms; 5 - cable winding drum; 6 - cabin; 7 – central current collector;9, 15 - dead-end limit switches; 10 - cable limit switch; 11,14 - mechanisms of movement; 12,13 - rail grips; 16 - transfer limit switch.

Figure 11.2

The engine room houses: a control panel, an operator station (OP27 display), AC electric motors for the lifting and closing mechanisms, electric motors for fans, brake pushers, frequency converters, a controller with intelligent input and output modules, a cable communication channel between the controller and control panels, and a station grab closure control.

The crane control system is based on a controller SIMATIC S7-400 companies Siemens. All mechanisms are controlled using industrial networks Sinec L2 And Profibus- D.P.. Communication between the main subsystems of the control system is carried out via an intelligent module ET200N and the above networks. The control system implements the following operating algorithms: control of the crane's lifting and closing drive, boom control, rotation control, crane movement control, rail grip control, simultaneous operation of several mechanisms, emergency mode.

Elevator control systems

The main parts of the elevator are: winch, cabin, counterweight, guides for the cabin and counterweight, shaft doors, speed limiter, traction ropes and speed limiter rope, pit components and parts, electrical equipment (including control system).

Various types of electric drives are used in elevator lifting mechanisms.

IN The unregulated drive uses one- and two-speed AC motors. A single-speed unregulated asynchronous drive is used in low-speed elevators with low requirements for the accuracy of stopping the car. The drive power circuit includes a single-speed asynchronous motor with a squirrel-cage rotor. Contactors ensure that the motor is turned on to move the cabin up and down by changing the phase sequence of the supply voltage. The electromagnetic brake is powered through a rectifier and ensures that the brake is released when the drive is turned on and the brake is activated when the drive is turned off when the cabin approaches the destination floor.

The two-speed asynchronous elevator drive uses a squirrel-cage motor with two high- and low-speed stator windings. In the low-speed winding of elevator motors, the number of pole pairs is usually three, four or six times higher than the number of pole pairs of the high-speed winding, which causes the synchronous speed to be reduced by the same number of times.

An adjustable DC drive provides similar conditions and is used to generate a motion pattern of the elevator car that is close to optimal, as well as high precision in stopping the car.

Modern elevators use two control principles: open and closed. With the open principle, signals generated in the logical control system (control station) are used to control the winch drive. Possible changes in the parameters of the cabin and winch during operation are not taken into account.

The closed-loop principle allows you to take into account all changes in parameters and control the drive using signals received from the logical control system, as well as take into account the results of the drive’s operation. As a result, the drive control system makes it possible to increase stopping accuracy and improve the smoothness of cab movement.

Frequency control system for asynchronous electric drive speedOVF 20 companiesOtis is made on the basis of PWM and consists of two main components: a control boardMSV II and power section. Functional diagramOVF 20 shown in Fig. 11.3.

The power part consists of a connection circuit to the electrical network and a converter consisting of an uncontrolled three-phase full-wave rectifier, a DC communication line and a three-phase inverter. The voltage of the three-phase electrical network is rectified and smoothed by a filter in the DC communication line, after which the transistor inverter using a given sequence switchingIGBT -transistors converts DC voltage via PWM into three-phase AC voltage with variable frequency. Transistors provide high switching speed (with a carrier frequency of 10 kHz).

Figure 11.3

Information about the output values ​​is received from the BR speed sensor located on the motor shaft. A two-channel (track) encoder is used with a signal phase shift of 90° GBA633 A1 (1024 pulses for each track). Controller MCS 220 exchanges signals with OVF20 (control signal VI... V4 , encoded by four bits; UIB, DIB, NOR– signals encoded by one bit each; elevator current state signals D.S.1 ... D.S.3 , encoded by three bits). Signals UIB, DIB, NOR represent data that determines the initial state of the system OVF 20 before operation, i.e. the elevator operates in up-down teaching mode or in normal mode.

The closed speed control loop guarantees precise and comfortable drive behavior at every moment of operation. The measured motor speed is input into a speed controller such as a PI controller. The dynamic accuracy of speed control (the time it takes for the speed control system to eliminate a speed error) is high.

The operating algorithm of the control system (Figure 11.4) consists of the main algorithm, the algorithm of subroutines that implement various operating modes of the control system (audit, release, control from the machine room, normal operation, fire hazard), and the algorithms of additional subroutines that implement standard actions performed in normal operation mode (elevator movement when ordered, car stopping on the floor).

Figure 11.4

The algorithm begins with turning on the elevator and operation (block1 ), after which continuous monitoring of the safety chain begins (2 ). If the circuit is open, it occursAvaemergency stop of the elevator (3 ). Depending on the reason for the emergency stop, the release mode is applied (5 ), if the elevator car is installed on safety devices or limit switches, or another type of failure in the system is determined and eliminated ( 6 ). Blocks7...9 determine the need to turn on one or another operating mode of the elevator, blocks 10...12 implement the corresponding subroutines. The program continues to operate until the elevator is forced to stop.

The algorithm diagram of the subroutine that implements the normal operation mode is shown in Figure 11.5.

Figure 11.5

In this mode, fire safety monitoring is carried out (2 ), registration and execution of all calls and orders, control of cabin load. This algorithm is designed taking into account the operation of a system with collective downward control, i.e. passing calls are made when the cabin moves down (if the load is less than 90% of the nominal), Thus Thus, the subroutine implements call waiting and registration (3 , 4 ),checking whether the elevator car is on the call floor (5 ). Depending on this, the doors of the cabin are opened with subsequent operation of the elevator by order (6, 7 ) or the cabin occupancy condition is checked (8 ). If the cabin is free, then the blocks 9… 20 select the direction of movement of the cabin and, depending on this, after receiving the order, passing calls are made when moving down (if they are registered) (14... 20 ) or movement of the cabin to the highest of the floors from which calls were received, and then, after receiving an order, collective control for movement down.

If the cabin is occupied when a call is registered, the call is made while the cabin is passing along, provided that it is loaded at less than 90% of the nominal load. Otherwise (Figure 11.6), wait until the cabin is free or proceeds in the same direction, less than 90% loaded. (21 ...29 ).