Suspended electric trolleys (electrified hoists, hoists and beam cranes) are used for lifting and moving loads and machine parts during installation and repair work inside industrial premises. Beam cranes are smaller than overhead cranes, which reduces the size of industrial buildings, and their maintenance does not require qualified personnel.
Suspended electric trolleys are designed for lifting and moving loads at production facilities along a strictly defined path.
To drive the load lifting mechanism at a speed of 6.5 - 6.9 m/s, an asynchronous motor with increased slip type AOS-32-4M is used (power 1.4 kW at 1320 rpm and duty cycle = 25%). The upward movement of the hook is limited by a limit switch.
To drive the running trolley, an electric hoist uses an asynchronous
electric motor type TEM - 0.25 (power 0.25 kW at 1410 rpm and duty cycle = 25%) The movement of the hoist along the beam in both directions is limited by mechanical stops.
The beam crane can move along the production premises, driven by an electric motor with a squirrel cage or wound rotor. The crane-beam bridge, which has a moving mechanism with an electric drive, is made in the form of a single beam along which an electric trolley moves.
To drive suspended electric trolleys, three-phase asynchronous motors with a squirrel-cage rotor are used, and only with a large load capacity and the need to regulate speed and smooth “landing” of loads - asynchronous motors with a wound rotor.
Due to the lack of low speed required for smooth landing of loads or precise stopping of the crane beam, the worker has to periodically turn on and off the electric motors, and this increases the number of starts and causes heating of the windings, and also reduces the wear resistance of the contacts. Therefore, some crane beams have electric drives for lifting and moving with two operating speeds: nominal and reduced, which are ensured by using two-speed asynchronous motors instead of single-speed ones or an additional microdrive.
Suspended electric trolleys with a low travel speed (0.2 - 0.5 m/s), driven by squirrel-cage motors, are usually controlled from the floor (ground) level using pendant push-button stations. In suspended trolleys and crane beams with an operator's cabin (at a movement speed of 0.8 - 1.5 m/s), wound-rotor motors are controlled using controllers.
The electric motors of the crane beams are controlled using reversible magnetic starters and start buttons suspended on a flexible armored cable.
The voltage to the coils and contacts of the contactors for lifting KM1 (Fig. 4), lowering KM2, moving forward KMZ and backward moving KM4 is supplied through a circuit breaker and cable or contact wires. The upward movement of the lifting device is limited by the limit switch SQ.
Figure 3.1 Electrical circuit diagram of the crane beam
Blocking of reversing motor contactors from simultaneous activation is carried out by double-circuit buttons and mechanical blocking of the contactors themselves (or by the contactor break contacts).
On electric hoists and overhead cranes, they do not use bypassing of the starting buttons with the corresponding closing blocking contacts of the contactors, preventing the possibility of the hoist continuing to operate after the operator releases the pendant push-button station. Simultaneously with the lifting motor, the electromagnet UA is turned on, opening the brake.
The operating mode of overhead crane beam engines depends on their purpose. If loads are moved to overhead cranes over short distances, then the engines operate in a shamefully short-term mode (for example, on trolleys serving areas of workshops or warehouses).
For crane beams transporting loads across the plant territory over relatively long distances, the operating modes of the lifting and moving motors are different: the former are characterized by a short-term mode, and the latter by a long-term mode. The power of the motors for lifting and moving electric hoists, hoists and crane beams is determined in the same way as for the motors of overhead crane mechanisms.
There are modifications of the crane with different span lengths, hook lifting heights and product lifting capacity. In this case, the crane span can vary from 4.5 to 22.5 m or more.
The crane's service area allows it to cover the maximum height of the workshop; The simplicity of the crane beam design allows it to be used for the mechanization of loading and unloading operations in mechanical engineering and warehousing.
The crane beam is intended for operation indoors or under a canopy at an ambient temperature of -20 to +40 degrees C (from -40 to +40 degrees C as agreed with the customer). The crane is powered from a three-phase alternating current network with a voltage of 380 V and a frequency of 50 Hz. The construction height of the crane depends on the construction height of the hoist and the height of the metal structure of the crane.
Control is carried out by the operator, from a pendant console (from the floor) or a remote control Additional options: Radio control up to 100 m, IP65, lightweight, battery powered. Frequency converter for smooth acceleration and the ability to change the speed of cargo transportation. Load limiter (on the hoist). Brake on the movement mechanism Micro speeds for lifting (depending on the selected hoist)
Specifications
Load capacity, t 1; 2; 3.2; 5; 10; 12.5; 16.0t.
Lifting height, m 6.0 - 36.0 and above
Span, m 4.5-22.5
Operating mode according to: - GOST 25835 3M
Lifting speed, m/min (depending on the choice of hoist) micro/main. 4, 6, 8, 12,16
1/4; 2/8; 3/12; 4/16
Crane travel speed, m/min 20.0; 24.0; 32.0
arbitrary speed (0-32.0)
Hoist movement speed, m/min
(depending on the choice of hoist) 12; 15; 20; 32;
12/4; 15/5; 20/6; 32/10
Climatic performance:
Standard
Low temperature
from -20C to +40C
from -40C to +40C
The operating cycle of an overhead support and suspension crane consists of three stages:
Grabbing and/or securing cargo;
The main working stroke is lifting, moving cargo, unloading;
Free idling without load - return of the lifting mechanism to its original position.
Working and idling motion on the movement graphs have three main characteristic sections: the beginning of work (acceleration), smooth movement and gradual braking. In this case, the places where acceleration begins and where braking ends are very important, since at these stages of the crane’s operation increased dynamic loads appear on the assemblies and components of the metal structures of overhead cranes.
To reduce the negative impact on crane mechanisms, we always advise customers to additionally equip beam and overhead cranes with frequency travel converters. Supporting and crane-suspended beams of large load-bearing capacity of long crane spans are especially sensitive to this. The service life of beam cranes using frequency controllers can be extended several times.
Figure 3.2 Electrical circuit for controlling a beam crane (frequency controller)
Table 3.1 - List of electrical circuit elements
Telpher device. Connection diagram for a 220 volt hoist
Electric hoist device, hoist equipment, hoist diagram.
The most popular and easiest to install and operate device for lifting loads is the electric hoist. Let's look at its design using the example of modern hoists of the MH series produced by Balkankarpodem. The general diagram of the hoist is shown in the picture above.
Schematic electrical diagrams of the hoist can be found here
The mechanical equipment of the MH electric hoist includes such important structural elements and assembly units as a lifting drum, gearbox, coupling, hook suspension, trolley, and load rope.
Lifting motor
Asynchronous two-speed electric motor with cone rotor and stator and built-in asbestos-free cone brake. The rotor has the ability to move with less resistance in the axial direction. In the event of a power failure, the brake is activated by the force of the coil spring. A wide range of possible combinations between motors and gearboxes with different technical characteristics expand the range of lifting loads and lifting speeds. Additionally, hoists are supplied with two-speed motors - having two stator windings (for operating speed and for precise positioning of the load). Another delivery option is with frequency converters for the smoothest possible starting and braking of drives.
Gearbox
Two-stage planetary gearbox installed on the opposite side of the electric motor. This design is preferred due to the need to ensure compactness of the hoist in the radial direction. Three stages of the gearbox provide reduction (reduction) of engine speed, as well as smooth starting and braking. High-quality materials are used for the manufacture of gears and other gear elements. The surfaces of the gear teeth are carburized and hardened, followed by grinding, which ensures a long service life and silent operation of the gears with high gear efficiency. An extended kinematic chain for transmitting engine torque to the drum reduces dynamic loads when operating an electric hoist.
Frame
The new body is box-shaped. It is a tightly welded flange-type connection between the engine and the gearbox. The rope output in all possible radial directions along the periphery of the housing ensures the operation of the electric hoist in a variety of mounting options and positions.
Elastic coupling
A special gearbox coupling is used, located inside the drum between the motor shaft and the gearbox shaft. The elastic package absorbs peak torque components. The design of the coupling ensures unhindered axial movement of the electric motor shaft. At the same time, it protects the shafts from any radial or tangential movements. This specificity is due to the fact that the rotor of the lifting electric motor is conical. When the drive is turned on, such a rotor extends along the axis, disengaging from the stator, and when turned off, it retracts back. Thus, the engine itself is able to brake the drive during a stop, that is, it has a built-in brake. The kinematic connection between the gearbox and the electric motor is unbreakable.
Drum
The lifting drum is a cylindrical hollow structure designed for winding a cargo rope. The surface of the drum is covered with special grooves - “streams”, thanks to which the cargo rope is wound in even rows, without overlaps or creases. Along with the rope, the rope layer also moves on the drum - a device necessary not so much for laying the rope in streams, but for turning on and off the limit switches for over-lifting and over-lowering.
Screw channels for the rope are made along the surface of the drum. A special rope wrap moves in these channels and ensures correct winding and unwinding of the rope, regardless of the size of the suspended load. The drum has two diaphragms. One of them is mounted on the front flange of the electric motor using a roller bearing. The torque from the outgoing hollow shaft of the gearbox is transmitted to the second diaphragm through a splined connection.
Rope wrap
New design. To replace the rope wrap, you do not need any special tools. The limits of rope deflection towards the engine or gearbox are ±4°. The rope tie operates the switch for the extreme upper and lower position of the hook.
Rope
The MH electric hoist uses a Bulgarian-made metal cable as a load rope. The most common rope reeving involves rigidly tying one end to the hoist body and clamping the second end to one edge of the lifting drum. In this case, the cargo rope itself is thrown through the hook suspension block. This reeving avoids damage to the rope and extends its service life. One end of the rope is fixed to the drum using rope ties. The other end is attached to the hoist body, or to the hook body, or to the drum first, depending on the method of hanging the load. The technical characteristics of the rope provide the necessary reliability and minimal wear on the rope itself and the drum channels.
Hook - set
Hook included: a new design that, together with the chain hoist, meets modern technical safety requirements. Operation is facilitated by the minimal dead weight of the hook. There is reliable protection against the arbitrary release of the rope from the channels of the rope rollers. The hook suspension contains a freely rotating rope block in a metal casing that prevents the rope from falling off. The cargo hook itself also rotates freely in both directions for the convenience of slinging work.
Trolleys
Three types of trolleys are offered: type N, type K and type D. Electric hoist bodies are attached to them in such a way that optimal load distribution is ensured on all wheels. The wheels are designed to move the hoist along the flanges of the I-beam. The trolleys can also be electric (EK), manually operated (RK) or free-wheeling (SK). The electric trolley has a motor mechanism of the same type as the load lifting mechanism. A normal motor mechanism with an electromagnetic brake is also available. The range of trolley speeds is very wide. Installation and adjustment of bogies in relation to the profile of the monorail are carried out smoothly. In case of ordering a double-rail trolley, the track width and dimensions of the rails are specified by the customer. Some electric hoists, which are large in the axial direction, are equipped with two running trolleys.
Electrical equipment
The electrical equipment of the hoists includes lifting motors, travel motors, a pendant control panel, a starting cabinet, a limit switch block, a brake coil and a load limiter. The coil and limiter, depending on the configuration, may be missing. The design of the electrical equipment of the hoist can be special, for example, for operation in a chemically aggressive environment or in a tropical climate.
The voltage and frequency of the electrical network are given by the customer. Operating voltage to the relay coil and contactors is 42 V, frequency -50 Hz. For the most part, the electrical equipment is located in a command box attached primarily to the hoist body. The limit switch for lifting and lowering the load is placed in the motor terminal block.
The push-button pendant control panel has a degree of protection of IP65 and can be four-button or six-button for operation as part of an overhead crane. The remote control includes a key mark to prevent unauthorized access to the control of the mechanism, as well as a mushroom button for emergency shutdown of the drives. For hoists with two-speed electric drives, the remote control may have two-position buttons (pushers) or a larger number of buttons - up to 12 pieces.
The rugged starting cabinet contains the magnetic reversing starters for actuating the drives, a rectifier for powering the brake coil (if equipped), terminal blocks for connections, an electronic unit for the load limiter (if equipped), and a 380/42 control circuit transformer. The starters are mounted on a DIN rail, but they are not available when controlling frequency converters.
The contacts of the lifting and lowering limit switches are installed in the terminal box of the lifting motor. The mechanical connection with the rope laying machine is provided by a special rod on which adjustment blocks are installed.
The braking electromagnetic coil of the MH hoist provides braking of the hoist drive along with the conical rotor. It is powered by direct current from the rectifier in the starting cabinet.
The load limiter for MH electric hoists is available as a separate order. It is electromechanical, and its design is simple and reliable. If an overload occurs, the limiter breaks its contacts in the ascent control circuit and then only descent is possible. The level of load capacity is adjusted mechanically with a special adjusting screw.
telfermag.ru
Electrical circuits
Purpose and design of electric hoists
An electric hoist is a small-sized winch, all the elements of which (electric motor, gearbox, brake, rope drum with threads for laying the rope, a cabinet with starting equipment and other necessary devices) are mounted in one housing or attached to this housing. The electric hoist also includes a chassis for moving along a monorail track and a hook suspension. As a rule, hoists are equipped with a pendant control panel for control from the floor.
Excluding manual hoists and car jacks, electric hoists are the most common lifting machines in the world.
Electric hoists are designed for lifting and horizontal movement of cargo along a monorail track indoors and under a canopy at ambient temperatures from -20 (-40) to +40°C.
Hoists are used as part of suspended and supporting single-beam, cantilever, gantry and other cranes, as well as monorails and independently.
Until the early 90s, a large amount of material handling equipment was produced in the Soviet Union, but the demand for this equipment always exceeded production. Electric hoists were distributed in 160-180 thousand units. per year (including approximately half of Bulgaria's production), and consumers asked for twice as much. The bulk of electric hoists are used to equip single-girder and jib cranes.
Electrical equipment of electric hoists
Electrical circuit diagrams of hoists with different designs have much in common and noticeable differences. They show the principle of design and operation of electrical equipment of hoists.
The hoists are powered from a three-phase alternating current network with a voltage of 380V and a frequency of 50Hz.
Electric hoists use magnetic reversing starters without thermal protection with electrical interlocking.
Electric hoists are controlled manually from the floor through a suspended push-button control station. The design of the push-button station is such that turning on the hoist mechanisms is possible only by continuously pressing the button.
The circuit for switching on the contacts of the control station buttons provides for an electrical interlock, which eliminates the possibility of simultaneous operation of the starters when buttons intended to turn on opposite movements of the same mechanism are simultaneously pressed. This does not exclude the possibility of simultaneous activation of different mechanisms (combining movement with lifting or lowering a load). The presented circuit diagrams retain the designations of the elements used in the operating manuals.
Electric hoist
Electrical circuit diagrams of hoists
Schematic electrical diagram of a hoist with a load capacity of 5.0 tons of the Slutsk PTO plant (developed in 1999).
The electric hoist is equipped with a disc brake, switches for the upper and lower positions of the hook suspension, and an emergency switch for the upper position of the suspension. 42V control circuit.
The power supply to the hoist must be carried out by a four-core cable, one of which is the grounding wire. When trolley powering the hoist, it is necessary to have a fourth grounding wire.
The hoist control circuit operates at a low safe voltage of 42V. which is obtained using a transformer (T) with separate windings connected to phases A and C. The secondary winding of the transformer (T) must be grounded.
Fuses (F1, F2, F3) protect the transformer windings. The key mark (S) of the PKT-40 control station ensures the activation of the hoist control system and the supply of voltage to the magnetic motor starters.
The hoist control buttons (at the station) (S1, S2, S3, S4) provide current supply to the coils (K1, K2, KZ, K4) of the corresponding magnetic starter. Each push-button element, due to its design, provides the first stage of electrical blocking from the simultaneous activation of reversing starters of one motor. The second stage of electrical blocking with the same function is provided by normally closed contacts of the starters (K1, K2, K3, K4). The limit switches (S7, S8) break the electrical circuit of the coils (K2-K1, K4-KZ).
The switches (S7, S8) are acted upon by a rope handler via a mechanical kinematic chain. The switch (S9) duplicates the action of the switch (S7). The brake coil is included in the section of phase B, has two sections, which are wound with two parallel wires, and connected so that the beginning of one (H2) is connected to the end of the other (F1), forming one common terminal, and the other ends of the sections (F1 and F2) connected to diodes (D1 and D2). The power part of the circuit provides power to the motors. This happens using the contact part of the reversing starters K1-K2 and KZ-K4.
Schematic electrical diagram of hoists with a load capacity of 0.25 tons from the Poltava plant (developed in the early 70s)
Electric hoists are equipped with a disc brake, switches for the upper and lower positions of the hook suspension, and an emergency switch for the upper position of the suspension. 42V control circuit
Schematic electrical diagram of hoists with a lifting capacity of 3.2 tons of the Barnaul Machine Tool Plant
The driver of the hoist lifting mechanism is pressed into the drum. The hoists are equipped with a column brake, a switch for the upper position of the suspension (can be equipped with switches for the upper and lower positions of the hook suspension, activated by the rope handler). There is no provision for reducing the control circuit voltage. Basic version with one lifting speed.
Schematic electrical diagram of hoists with a lifting capacity of 5.0 tons of the Kharkov PTO terminal
The hoists are equipped with a limit switch for the upper position of the hook suspension. Hoists designed for installation on single girder cranes are supplied with a six-button control panel.
Current supply to electric hoists
The current supply to the hoists is carried out in most cases by a flexible cable (Figure 4.8). Trolley feeding is also possible.
A flexible cable (1), used to power the hoist (a four-core flexible copper cable in rubber insulation), perhaps with a current supply length of up to 25-30 m, is suspended using rings on a string (2). This design is shown in the figure.
Current supply to hoists using a flexible cable
The string used is 5 mm steel or brass wire or steel rope. Rings (3 and 4) - 40 ... 50 mm. The clamps (5) must not have sharp edges and are equipped with a coupling bolt (6). The lining (7) can be made of a rubber tube.
The distance between the hangers with a tensioned cable should be in the range of 1400 - 1800 mm. To prevent cable breakage, a soft steel cable with a diameter of about 2.5 mm, the length of which is slightly less than the length of the cable itself, is fixed together with it in the clamps, so that the tension is transmitted through the cable and not through the cable.
If the path of movement of the hoist is within 30-50 m, an I-beam or other rigid guide is used as a guide. In this case, the cable is suspended on roller hangers.
If the travel distance of the hoist exceeds 50 m, the possibility of using a simple and cheap cable current supply should be checked by calculation. The calculation should confirm the admissibility of the magnitude of losses in a long cable and the ability of the hoist without a load to overcome the resistance to movement of rings or carriages over the full length of the current supply. In some cases, with a small cross-section of the conductors of the current-carrying cable (with low transmitted power), with artificial weighting of the hoist without a load, etc. it is possible to increase the length of the cable current supply to 60 m or more.
When using trolley power, which is used for long travel distances of hoists and when operating hoists on tracks with turns (as part of monorails or independently), the current collector can be installed on either side of the monorail. For trolley power supply, a small-sized closed busbar or trolley route, designed according to the PUE, should be used.
www.electromontag-pro.ru
Starter connection diagram - Articles on electrical engineering - Catalog of articles
This is the simplest starter circuit (simplified version), which underlies all, or at least most, starting circuits for asynchronous electric motors, which are used very widely, both in industry and in everyday life. A bad electrician is one who does not know this circuit (strangely enough, there are such people). Although you probably know the principle of its operation, to refresh your memory or for beginners, I will still briefly describe this work. And so, the entire circuit except the electric motor, which is installed directly on a specific equipment or device, is mounted either in a panel or in a special box (PML).
The START and STOP buttons can be located either on the front side of this panel or not (mounted in a place where it is convenient to control the work), or maybe both, depending on convenience. Three-phase voltage is supplied to this panel from the nearest power supply point (as a rule, from the distribution board), and from it a cable goes to the electric motor itself.
Starter circuit simplified version
And now about the principle of operation: three-phase voltage is supplied to terminals F1, F2, F3. To start an asynchronous electric motor, the magnetic starter (PM) requires activation and the closure of its contacts PM1, PM2 and PM3. To trigger the PM, it is necessary to apply voltage to its winding (by the way, its value depends on the coil itself, that is, what voltage it is designed for. It also depends on the conditions and place of operation of the equipment. They come in 380V, 220V, 110V, 36v, 24v and 12v) (this circuit is designed for a voltage of 220v, since it is taken from one of the available phases and zero). Power supply to the coil of the magnetic starter is carried out through the following circuit: From f1, the phase enters the normally closed contact of the thermal protection of the electric motor TP1, then passes through the coil of the starter itself and goes to the START button (KN1) and to the self-pick-up contact PM4 (magnetic starter). From them, power goes to the normally closed STOP button and then closes to zero.
To start, you need to press the START button, after which the coil circuit of the magnetic starter will close and attract (close) contacts PM1-3 (to start the engine) and contact PM4, which will make it possible, when the start button is released, to continue working and not turn off the magnetic starter (called pick-up). To stop the electric motor, you just need to press the STOP button (KN2) and thereby break the power supply circuit of the PM coil. As a result, contacts PM1-3 and PM4 will be turned off, and work will be stopped until the next start. For protection, thermal relays must be installed (in our diagram this is a TP). When the electric motor is overloaded, the current increases accordingly, and the motor begins to heat up sharply, until it fails. This protection is triggered precisely when the current in the phases increases, thereby opening its contacts TP1, which is similar to pressing the STOP button. These cases occur mainly when the mechanical part is completely jammed or when there is a large mechanical overload in the equipment on which the electric motor operates. Although it is not uncommon for the engine itself to become the cause, due to dried out bearings, poor winding, mechanical damage, etc. I think for those who didn’t know this, this article: Starter circuit, simplified version, was very useful and one day it will come in handy more than once in life.
Starter connections according to the diagram - reverse
A variant of the above circuit is used to start electric motors operating in the same mode, i.e. without changing rotation (pumps, circular motors, fans). But for equipment that must work in two directions, such as a crane - beams, hoists, winches, opening and closing gates, etc., a different electrical circuit is required. For such a scheme, we will need not one, but two identical starters and a three-button START-STOP button, i.e. two START buttons and one STOP. In reverse circuits, remote controls with two buttons can also be used; these are areas where operating intervals are very short. For example, a small winch, operating intervals of 3-10 seconds, for the operation of this equipment, the option with two buttons is more suitable, but both buttons are start, i.e., only with normally open contacts, and in the circuit the block contacts (pm1 and pm2) are not self-retaining are activated, namely, as long as you hold the button pressed, the equipment works, as long as you release it, the equipment stops. Otherwise, the reverse circuit is similar to the simplified version circuit.
Starter connections according to the reverse diagram
Star-delta starter
Switching the motor from star to delta is used to protect electrical circuits from overloads. Mostly powerful three-phase asynchronous motors from 30-50 kW, and high-speed ones ~3000 rpm, sometimes 1500 rpm, are switched from star to delta.
If the engine is connected in a star, then a voltage of 220 Volts is supplied to each of its windings, and if the engine is connected in a triangle, then a voltage of 380 Volts is supplied to each of its windings. Here Ohm’s law “I=U/R” comes into play; the higher the voltage, the higher the current, but the resistance does not change.
Simply put, when connected to a delta (380), the current will be higher than when connected to a star (220).
When the electric motor accelerates and reaches full speed, the picture completely changes. The fact is that the engine has power that does not depend on whether it is connected to a star or a delta. Engine power depends largely on the iron and wire cross-section. Another law of electrical engineering “W=I*U” applies here.
Power is equal to current multiplied by voltage, that is, the higher the voltage, the lower the current. When connected to a delta (380), the current will be lower than to a star (220). In the engine, the ends of the windings are brought out to the “terminal block” in such a way that, depending on how the jumpers are placed, the connection will be a star or a triangle. Such a diagram is usually drawn on the lid. In order to switch from star to delta, we will use magnetic starter contacts instead of jumpers.
Star-delta scheme
Connection diagram for a three-phase asynchronous motor, in the starting position of which the stator windings are connected by a star, and in the operating position by a triangle.
There are six ends suitable for the engine. The KM magnetic starter is used to turn the motor on and off. The contacts of the magnetic starter KM1 work as jumpers to turn on the asynchronous motor in a triangle. Please note that the wires from the motor terminal block must be connected in the same order as in the motor itself, the main thing is not to confuse them.
The KM2 magnetic starter connects jumpers for star connection to one half of the terminal block, and voltage is supplied to the other half.
When you press the “START” button, power is supplied to the magnetic starter KM; it is triggered and voltage is supplied to it through the contact block; now the button can be released. Next, voltage is supplied to the time relay RV, it counts the set time. Also, voltage is supplied through the closed contact of the time relay to the magnetic starter KM2 and the engine starts in the “star”.
After the set time, the RT time relay is activated. Magnetic starter P3 is turned off. Voltage is supplied through the contact of the time relay to the normally closed (closed in the off position) block contact of the magnetic starter KM2, and from there to the coil of the magnetic starter KM1. And the electric motor is switched into a triangle. The KM2 starter should also be connected through a normally closed contact block of the KM1 starter, to protect against simultaneous activation of the starters.
It is better to take double magnetic starters KM1 and KM2 with a mechanical lock for simultaneous activation.
The “STOP” button turns off the circuit.
The circuit consists of: - Automatic switch; - Three magnetic starters KM, KM1, KM2; - Start – stop button; - Current transformers TT1, TT2; - Current relay RT; - Time relay RV; - BKM, BKM1, BKM2 – block contact of its starter.
elektromehanika.org
Electrical circuit of an electric hoist
Schematic electrical diagrams of the hoist.
To control electric hoists, reversible contactor circuits are used. Schematic diagrams of Bulgarian electric hoists for the MN and MNM series are presented in the tables below.
| The purpose of contactors is shown in circuit diagrams by applying the following symbols under the designations of the coils: | |
| Symbol | Purpose of the contactor |
| Contactor for “LIFT UP” movement at main speed – K1 | |
| Contactor for “LIFT UP” movement at micro speed – K3 |
|
| ↓↓ | Contactor for “DOWN” movement at main speed – K2 |
| ↓ | Contactor for movement “DOWN” at micro speed – K4 |
| ←← | Contactor for movement “LEFT” at main speed – K5 |
| Contactor for movement “LEFT” at main and micro speeds – K5 |
|
| Contactor for movement “RIGHT” at main speed – K6 | |
| Contactor for movement “RIGHT” at main and micro speeds – K6 | |
| Contactor for movement “LEFT” and “RIGHT” at main speed – K7 |
|
| ← → | Contactor for movement “LEFT” and “RIGHT” at micro speed – K8 |
L1, L2, L3 – phases of the electrical network
S1 – emergency stop button T1 – transformer for operating circuit Q – main contactor (switch) F1, F2, F3 – fuses
Buttons: S2 - button for movement “DOWN” S3 - button for movement “LIFT UP” S4 - button for movement “RIGHT” S5 - button for movement “LEFT” S6 - limit switch
M - electric motor K1 – K8 – contactors K9 – time relay contactor B1 – electronic load limiter unit
tali.by
The operating principle of an electric hoist.
The diagram of the power part of the electric hoist is shown in Fig. 1. It consists of power contacts of two reversible magnetic starters KM1 and KM2, an electric motor for the winch cable drum M1 and a running electric motor M2. To prevent the load from lowering spontaneously, the shaft of the M1 motor is equipped with brake pads, and during operation of this motor, the solenoid with the brake coil YB1 opens the pads. Power supply and protection of the circuit from high currents and short circuits is carried out by the QF1 circuit breaker.
The control circuit diagram is shown in Fig. 2. It includes coils of magnetic starters KM1 and KM2 and a push-button station (highlighted in the figure with a dashed line), consisting of double four buttons SB1-SB4 and a key SA1.. The control circuit receives power from a single-phase network, from short circuits and high currents it is protected by fuse F1.
It is not difficult to understand the operation of an electric hoist. First, we supply power to the power contacts of the magnetic starters and the key contact of the control circuit for turning on the QF1 machine. Then we insert the key into the socket of the push-button station, closing contact SA1, thereby bringing the “phase” to the buttons. Next, we will consider the action of the circuit when buttons are pressed.
Let's say that to raise the load up, we press the SB1 button. The current will flow to the KM1v coil through the normally closed contacts of the SB2 button and the KM1n block contacts. the coil will be excited and draw into itself a steel core on which power movable contacts are installed, which close the motor circuit; the brake coil YB1 will turn on and release the winch rotor, the engine will start and the load will go up. This will happen until we release the button. Then the KM1v coil will be de-energized, its contacts will return to their original position; As a result, the M1 engine will stop, and the brake coil will turn off and its pads will press the engine rotor again. To prevent accidental pressing of two buttons SB1 and SB2, SB3 and SB4 at the same time, the circuit provides double blocking. When we press, for example, the SB1 button, the second contact of this button opens the circuit of the second coil of the magnetic starter KM1n; also, when the first KM1v coil is turned on, its block contacts of the same name break the circuit of the second coil, thereby preventing the activation of two “up” and “down” buttons at the same time.
The process of working with the remaining buttons is similar to the first one. To prevent the hook from being raised higher than it should be and creating emergency situations, a limit switch SQ1 is provided, connected to the break of the KM1v coil.
In order to prevent accidents as a result of sticking contacts of starters or other incidents, the QF1 circuit breaker is installed as close as possible to the operator.
Figures 3 and 4 show options for turning on an electric hoist using an additional magnetic starter KM1 and a step-down transformer installed inside the electrical panel of the hoist. The starter is designed to switch the voltage of an electric hoist. Now, in order to remove power from the hoist control starters, it is enough to pull out the key located on the push-button station. Thanks to the transformer, the buttons receive a reduced voltage that is galvanically isolated from the network, which makes the operation of the hoist safer.
In this article you will learn how to connect a beam crane to the power system.
To connect the crane beam, control and installation diagrams are used, showing the algorithm for connecting the main components of the structure. Electrical equipment of lifting bridge equipment includes: three-phase asynchronous motor, electric trolley, load-handling device, power cables.
The lifting mechanism includes a hoist for lifting and lowering the load, a trolley for moving and crane tracks.
Fig.1. Schematic diagram of the crane beam
The hoist (telpher) includes the following elements:
Propulsion unit, reduction gearbox,
Electromagnetic braking system to stop the shaft during power outages,
Load limiters,
Pull block blocks
On crane beams, additional lifting motors are often installed with two operating speeds: nominal and reduced.
This reduces heating and contact wear.
Most models have a push-button-cable control system. The signal is transmitted to reversible magnetic starters, which are suspended on a flexible cable. To prevent spontaneous activation, double-link interlocks are installed.
Rice. 2. Connecting the crane beam
How to connect a beam crane with 6 buttons can be found in the diagram supplied with the crane at the factory. It indicates the connection of motors to reversible pairs of starters, to which commands are sent from soft buttons.
The operation of radio-controlled devices is not fundamentally different from supplying power through cables; the only difference is in the method of supplying signals to the contactors. The basic control diagrams for radio remote controls are kept secret by most companies, so they cannot be found in the public domain.
However, the manufacturer is required to provide a complete list of design and installation documentation when the product leaves the factory.
The installation of a crane mechanism inside or outside a building depends on a number of factors:
- The type of command used.
- Number of electric motors and lifting devices.
- Sequences of connecting conductors and main components.