Magnetic starter– a switching device designed to connect a load (most often electrical machines) to the power supply network. Magnetic starters are available in each electrical diagram that starts, stops or regulates the speed of the electric motor. However, the widespread magnetic starters led to their use in everyday life. Therefore, many may be faced with the need for maintenance or repair of a magnetic starter.
First, let's look at magnetic starter design. The main components of a magnetic starter are: electromagnet coil, contact group(moving and fixed contacts, auxiliary and power), plastic housing. The moving contacts are mechanically connected to the coil core. The power contacts are designed for the rated current of the magnetic starter (when connecting an electric motor, the stator current). Auxiliary contacts are used to connect control circuits. In addition, it is possible to use attachments for magnetic starters, allowing you to expand the number of auxiliary contacts. Magnetic starters can be equipped with a thermal relay, as well as with control buttons on the device body.
When carrying out maintenance (repair) of a magnetic starter, you must:
1.
Carry out an external inspection of the magnetic starter to identify mechanical damage to the housing; checking the presence of all parts of the magnetic starter. Missing parts can directly affect the performance of the magnetic starter.
2.
Inspect the mechanical part of the magnetic starter, namely: the working spring and the electromagnet armature. When checking the anchor, there should be no jamming or difficulty in its movement.
3.
Clean the contacts. Cleaning the contacts of the magnetic starter should be done if there are obvious traces of carbon deposits or melting using a needle file. The use of sandpaper to clean contacts is strictly prohibited.
4.
Check that there are no short circuits between individual contacts of the magnetic starter and no short circuits between the contact and the metal body of the magnetic starter.
5.
Inspect the starter coil. The coil of the magnetic starter should not have chips, cracks, traces of soot or melted insulation. Defects in the magnetic starter coil can lead to increased noise during operation of the device. In addition, increased noise may be caused by insufficient line voltage or too much return spring force.
6.
Inspect the thermal relay (if equipped). First of all, you should pay attention to the setting value of the thermal relay.
Magnetic starter repair, as a rule, comes down to replacing individual contacts, a coil, a return spring or the body of the device.
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- December 15, 2018
- December 22, 2017
1. Inspection of contactors. Contactors must be cleaned of factory grease, dust, dirt and wiped with a dry and clean cloth. Compliance with the design of the type and nominal data of the contactor, and the integrity of all electrical connections are checked. Loose fasteners are tightened. The moving system is tested by hand to ensure there are no jams. The simultaneous closing and opening of the main contacts and the correct operation of the auxiliary contacts are checked.
If frozen drops of copper are detected on the contact surfaces, they are cleaned with fine glass (but not sandpaper) paper or a velvet file. Lubrication of contact surfaces is not allowed, since it burns out from the arc and contaminates the contact surfaces with combustion products, which. increases contact heating. When cleaning contact surfaces, it is necessary to strictly maintain the original shape (radius of curvature, profile) of the contacts in order to maintain their required rolling. It is necessary to clean only drops and sagging until the surface is leveled, but not until the shells are removed.
The contacts should touch linearly across the entire width without gaps, gradually rolling when closing with slight sliding. During operation, this will help maintain their surface in good condition.
2. Measuring and adjusting the pressure on the contacts. Checking the openings, dips and pressing of the main and auxiliary contacts is carried out on powerful and critical contactors; if necessary, they are adjusted.
Solutions, contact failures and contact pressures must comply with the requirements of Table. 6-1. and 6-2. The solution A and dip B of the main contacts are measured with a template or bore gauge in the places shown in Fig. 6-1, For bridge auxiliary contacts, these locations are given in Fig. 6-2.
The locations for measuring the initial and final pressing of the main contacts are shown in Fig. 6-3; pressing force values are contained in the table. 6-1 and 6-2. The initial pressing force on the auxiliary contact bridge should be in the range of 0.58-2.4 N (greater value for larger contactors), the final force is about 3 N.
Contact failure is determined by measuring the gap with closed contacts from the moving contact to its stop.
The initial pressure is adjusted by changing the initial compression (extension) of the built-in contact spring, changing its length by changing the number of washers or adjusting bolts; in some cases the spring needs to be replaced.
For contactors with spark-extinguishing contacts, it is necessary to check the distance between the main contacts at the moment the spark-extinguishing contacts touch, for which the armature of the magnetic system of the contactor is slowly brought to the core by hand until the spark-extinguishing contacts touch. The gap between the main contacts at this moment should be at least 1.5 mm.
If this distance is less, then the contacts should be replaced or adjusted with bolted connections according to the factory instructions.
3. Checking the pull-in voltage and contact drop-out It is convenient to produce according to the diagrams in Fig. 6-4. Package switch Q, bypass contactor auxiliary contact KM1 when determining the drop-out voltage, must be open. In the absence of a regulating autotransformer, you can use 220/36 V transformers by connecting them according to the autotransformer circuit (Fig. 6-5). With this connection, the voltage on the contactor coil will be equal to the minimum permissible operating voltage (0.85 U n) networks.
The main feature of the contactor switching process AC is a significant increase in the coil inductance as the air gap decreases. The total resistance of the coil is determined mainly by its inductive resistance, and therefore the coil current at the moment of switching on, when the inductive resistance is small, is 10-15 times greater than when the armature is pulled up. Unlike coils DC heating of AC coils has almost no effect on the change in magnetomotive force and on the pull-in voltage due to the small influence of the active resistance of the coils on the current. Therefore, during testing, no correction is made for the temperature of the coils and environment. For the same reason, checking the pull-in voltage of AC contactors requires that the operation be carried out quickly enough to avoid overheating of the coils and adjusting devices by the switching current. It should also be remembered that when checking the pull-in voltage from temporary low-power sources of operational current, significant voltage drops are possible at the moment of switching on and the data on the pull-in voltage turn out to be greatly overestimated.
The pull-in and drop-out voltages of DC contactors must be checked with the pull-in coil heated to a nominal permissible temperature of 70 °C. When taking measurements from a cold state, to clarify the results, it is necessary to make a correction for the deviation of the ambient temperature from 20 °C; Every ±10°C corresponds to a change in the pull-in voltage by ±2.5-3% of the rated voltage.
Contactors should switch on clearly when 85% of the rated voltage is applied.
The contactor dropout voltage is not limited by standards. It must be measured and entered into the protocol.
According to PUE-76 (§ 1-8-34), checking the pull-in voltage of contactors is not necessary, and contactors are tested by repeated switching on and off with reduced voltage: for switching on 0.9 U n 5 times, to turn off 0.8 U n 10 times. This test can be replaced by checking the operation of contactors during comprehensive testing of circuits, when the voltage of the operating current source is reduced to 80% of the rated one.
4. Checking the magnetic system. When the AC contactor coil is turned on at rated voltage, a strong humming noise may occur from the contactor, indicating a problem with its magnetic system. To eliminate a malfunction of the magnetic system, it is necessary to check the cleanliness of the contacting surfaces of the armature and the core, the absence of preservative lubricant, the accuracy of the fit of the moving and stationary parts of the magnet, the presence of an intact short-circuited turn laid in the slots of the core.
To check the tight fit of the armature to the yoke, a piece of copy paper and a piece of thin white paper are placed between them, and the contactor is closed manually. The size of the spot on the white paper is used to judge the quality of the anchor's fit. If both halves of the magnetic system are in contact with only a part of less than 60-75% of their surface, and in other places there is a gap (more than 0.03-0.05 mm), then the armature needs to be adjusted.
The short-circuited turn is made solid (without joints) or welded (soldering is not allowed) and must be tightly clamped in its groove. The coil is fastened by bending the plates intended for this purpose, driving narrow wedges into the groove, or punching the edge of the groove. Replacing the material of a short-circuited turn, changing its cross-section or medium length are unacceptable, since in these cases the coil can overheat so much that it overheats the coil and the contactor begins to hum. Normal temperature heating the short-circuited coil to 200 °C.
5. Checking the contactor with a latching mechanism. In Fig. Figure 6-6 shows a control diagram for a contactor with a latching mechanism. When a pulse is given to turn on the contactor, the retractor coil KM1 receives power via a normally closed auxiliary contact KM2.1 latch mechanism, attracts the contactor armature and the latch lowers; latch auxiliary contact KM2.1 opens the retractor coil circuit, and the auxiliary contact of the latch KM2.2, closing, prepares a shutdown circuit. When disconnected to the retractor coil KM1 voltage is applied simultaneously with the latch coil KM2. The retractor coil attracts the contactor armature and thereby removes the force created by the armature in the on position from the latch and allows the coil KM2 Easy to lift the latch. After lifting it with contact KM2.2 the contactor turns off and returns the circuit to its original position.
When inspecting a contactor with a latching mechanism, it is necessary to check the operation of the latter by manually turning on the contactor. When checking the operation of the contactor under voltage, the operation of the latch contacts is also checked. In case of unsatisfactory extinguishing of the arc on the auxiliary contacts KM2.1 The latches connect a capacitor with a capacity of 1 µF (250 V MBGCH type for a 220 V network) in parallel with them.
Electromagnetic starters are intended for use in stationary installations for remote starting by direct connection to the network, stopping and reversing three-phase asynchronous electric motors with a squirrel-cage rotor of alternating voltage 660 V, frequency 50 and 60 Hz. In the presence of three-pole thermal relays of the RTT and RTL series, the starters protect controlled electric motors from overloads of unacceptable duration and from currents arising when one of the phases is broken. The starters are suitable for operation in control systems using microprocessor technology when the switching coil is bypassed with an interference suppression device or with thyristor control.
Designed for remote start by direct connection to the network and shutdown of three-phase asynchronous electric motors with a squirrel-cage rotor. Additional features: reversing, in the presence of thermal relays - protecting motors from overloads of unacceptable duration, including those arising when one of the phases fails, changing the circuit diagram for switching on the Y/A windings.
Maintenance
During the period between repairs, maintenance of electrical devices is carried out, which is a set of operations or an operation to maintain the functionality or serviceability of the device during intended use, standby, storage and transportation. The device is not disassembled.
The typical scope of work for maintenance Magnetic starters include: cleaning of dust and dirt, lubricating rubbing parts, eliminating visible damage, tightening fasteners, cleaning contacts from dirt and deposits, checking the serviceability of casings, shells, housings, checking the operation of signaling and grounding devices.
It is recommended to check and adjust thermal relays in the laboratory using special electrical devices. Checking the relay begins with an external inspection: checking the presence of seals, the integrity of the casing and its tight fit to the base, the condition of the seals, and cleaning the relay.
After removing the casing, they begin an internal inspection: clean the parts, check the tightness of screws, nuts, fastening springs, contacts, bearings, magnetic circuits; check the reliability of internal connections; adjust the mechanical part of the relay; the contacts are thoroughly cleaned and polished with blued material (needles or abrasive materials should not be used).
Next, measure the insulation resistance with a 1000 V megohmmeter between the electrical parts of the relay and the housing, which must be at least 10 MOhm, and check the settings. If defects are found that are beyond the ability to eliminate them in the laboratory, the relay is replaced with a new one.
Repair work
As a result of operation, accidents, overloads and natural wear and tear, some electrical equipment and networks fail and must be repaired.
In electrical devices, moving, fixed and arcing contacts are most often damaged. Repair mainly consists of identifying the malfunction, eliminating it, replacing damaged and worn parts, followed by adjustment and testing. During operation, the contacts are cleaned of metal deposits, soot, and oxides. Clean with a file with a fine (fine) notch. Eliminates strong and weak contact pressure. To do this, place paper (foil) between the contacts, pulling the movable contacts through a dynamometer and pulling out the foil. Normal force is 0.5–0.7 kg. The magnetic contact system can create noise, humming, the reasons for this are: the armature does not fit tightly to the core, damage to the short-circuited turn, very high contact tension, the armature is skewed in relation to the core, there is rust in places where the armature and core touch, magnetic starters and contactors should not be allowed different times of closing power contacts. Short-circuited turns for contactors and magnetic starters are made of copper, brass and aluminum. They fit into stamped grooves at the ends of the core. Attention is drawn to arc chutes. Their absence can cause the arc to overlap individual phases. Coils are repaired in case of frame damage, breaks, turn short circuits and complete combustion. A break in the coil is detected if no traction force is developed and no current is consumed. A turn fault is detected by abnormal heating and decreased thrust.
For contactors, main contacts, flexible connections, arc chutes, coils, springs, and short-circuited turns are often replaced. The insulation resistance of the windings should not exceed 0.5 MOhm. The heating elements of the relay burn out more often. Nichrome and fechral are used for heating elements. Individual heating elements are made by stamping. Spiral heating elements are cadmium coated to protect against oxidation.
Contact repair. Contamination, wear, burning, soot or oxidation, deposits and splashes of metal on the surface of moving (including switch knives) or fixed (knife jaws) contacts, as well as on plates and contact bridges, are eliminated with a cotton napkin soaked in gasoline or a file. When the thickness of the contacts is less than 50% of the original value, the burnt contacts are replaced with new ones. Contacts that have a metal-ceramic (silver-nickel) or other coating that provides increased conductivity or corrosion resistance are not allowed to be cleaned with a file or needle file! Contacts are cleaned with a cotton cloth soaked in gasoline, and especially critical contacts (6–10 kV switches, relays) with alcohol. Use a finely cut file, needle file or glass sandpaper to clean or remove deposits and deposits of metal on uncoated contacts. The contact surface must be clean; cavities with an area of no more than 1 mm2 and a depth of up to 0.2 mm are allowed. The thickness of the jaws and knife switches should not be less than 80% of the original.
If the contact springs are broken or weakened, or the anti-corrosion coating is damaged, the springs are replaced.
Repair of electromagnet coils. Reels can be framed or frameless. The most common damage is cracks up to 15 mm long in the frame. They are eliminated as follows. The surface of the frame around the crack is cleaned of dust and oil with a cotton cloth soaked in gasoline. A layer of BF glue is applied to the surface of the crack and dried in air for 10–15 minutes, then a second layer is applied and left for another 5–10 minutes. After this, the glued parts of the frame are tied together with taffeta or cotton insulating tape and dried in an oven for 1.5–2 hours at a temperature of 100–110 ° C, after which they are cooled and the bandage is removed.
If the insulation resistance is low (less than 0.5 MOhm), the coil is placed in a drying cabinet at a temperature of 60–70 °C for several hours. After this, the insulation resistance is checked and, if the standard is reached (at least 1 MOhm), it is immediately impregnated with one of the BT-988 or BT-987-M varnishes and dried a second time for 8 hours at a temperature of 105 ° C.
If the outer layer of the coil insulation is damaged or the winding wire breaks in the upper layers of the winding, remove the outer insulation of the winding and the damaged turns to the point of damage or breakage, solder, insulate the soldering area of the new winding wire and wind the required number of turns, repeating the operations that are performed when winding new coils .
In case of significant damage to the frame, interturn short circuits, or burning of the winding insulation to a great depth, the coil must be replaced with a new one.
Repair of frame reels. Select the frame and wire required for the coil, the parameters of which must correspond to the passport data. The ends of the coil wire are cleaned with sandpaper, tinned and soldered with POS-30 solder to the output conductor. The terminal consists of a sheet or brass part with a conductor of a larger cross-section than the winding wire soldered to it to ensure the mechanical strength of the terminal. The soldering area is insulated.
Before installation on the winding machine, the frame should be wrapped in a double layer of electrical insulating paper with a thickness of 0.02–0.03 mm and the end should be glued to the frame. When winding, you must ensure that the tension on the wire is not excessive, as this may cause the wire to break. When winding, the wire should lie in an even, dense layer. Between the 1st and 2nd layers of the winding, interlayer insulation made of insulating paper is laid. If the coil is heat-resistant, then thin fiberglass fabric is used for interlayer insulation.
The winding terminals can be soft or hard. Soft ones are made from flexible mounting wires. The place where the soft lead is soldered to the winding is insulated with a polyvinyl chloride tube, onto which a strip of varnished cloth is applied.
Rigid leads, as indicated above, are made from pre-tinned brass strips. They are isolated from the winding by gaskets. The leads soldered to the coil are secured with threads. The soldering points are wrapped with an insulating gasket that has a cutout for the vertical part of the terminal.
Repair of frameless reels. A split mandrel is made according to the dimensions of the defective coil. Its size, taking into account the insulation of the coil, must correspond to the core for which the coil is intended. The mandrel is installed on lathe and secured to a special winding device. A taffeta tape is placed on the mandrel in four places around the perimeter in such a way that after winding the coil it is enough to construct a bandage. Using taffeta tape, the mandrel sleeve is wrapped in two layers of electrical cardboard with a thickness of 0.2–0.3 mm and a width equal to the height of the coil. A piece of flexible copper wire is soldered to the beginning of the winding with POS-30 solder. The soldering area is insulated with a micanite strip.
When winding a coil, each layer is covered with impregnating varnish and thin electrical paper 5–7 mm wide than the height of the coil. These edges of the paper are wrapped under the outermost turns of the next layer of the coil.
A piece of flexible wire is also soldered to the end of the winding for output. The coil is banded with previously laid taffeta tape. The manufactured coils are dried for 2 hours in a drying oven at a temperature of 80–90 ° C, the insulation resistance and integrity of the winding are checked. Immediately after drying, while still warm, the coil is dipped into an impregnation bath with ML-92 varnish and held until bubbles stop, after which it is dried again for 4–5 hours at a temperature of 100–110 °C. The dried winding of the coil is wrapped with two or three layers of insulating paper, two layers of varnished fabric or taffeta tape, the terminals and frame are cleaned of the varnish layer, and a tag is stuck on.
The insulation of a coil ready for use is tested with an alternating current voltage of 2000 V with a frequency of 50 Hz for 1 minute, gradually increasing the voltage. The insulation resistance of the coil after testing should not be less than 0.5 MOhm.
Repair of magnetic circuit. Contaminants are removed with a cotton cloth soaked in gasoline; traces of corrosion are thoroughly cleaned with a steel brush and sandpaper; hardening on the contact surfaces of the core and yoke is removed by grinding the surface with a file on a grinding machine.
The area of contact between the core and the yoke is checked as follows: take sheets of white and carbon paper folded together, compress the yoke and the core with a certain force, and get an imprint of the contact area on the paper, which must be at least 70% of the area of the core. The tightness of the fit is checked with a 0.05 mm feeler gauge. The probe should not enter the space between the yoke and the core more than 5 mm. Places of unevenness are scraped along the steel sheets.
The damaged short-circuited turn is replaced with a new one, made to the size of the defective one from the same material. The damaged coil is sawn and removed. The coil grooves are cleaned with a file and the coil is secured in the grooves.
The reduced value (less than 0.2 mm) of the non-magnetic (air) gap between the middle cores of the core and the yoke of the magnetic circuit is brought to the norm of 0.2–0.25 mm by filing the middle core of the yoke (or core), which is checked with a probe. Non-parallelism of planes is allowed within 0.01 mm.
The cleaned core and yoke are immersed in a bath of GF-92-ХС enamel so that the surfaces of their contact are not varnished. Painted parts are air dried.
In most electric drive control circuits, contactors, as well as magnetic and contactless (thyristor) starters are used to turn on motors. With their help, remote and automatic switching on and off of the drive motor, starting and control resistances, switching off emergency sections of the network, switching on brake electromagnets and other auxiliary devices is carried out.
Contactors and starters are most often completed by manufacturers along with control and protection equipment in special blocks, panels, switchboards and control stations in accordance with design diagrams and are supplied to the consumer tested and adjusted. Magnetic starters are often delivered in bulk for installation, and then the design circuit is installed completely on site.
Contactor and relay equipment supplied for installation, in most cases, requires preliminary checking and mechanical adjustment, since the fastenings may become loose during transportation, and long-term storage Corrosion may form, causing the moving systems to seize and impair the conductivity of the contact surfaces.
During the initial setup of devices at the installation site, they are checked by external inspection: compliance of the type of device and the parameters of the retractor coil with the design or actual loads, the absence of preservative lubricant and transport fastenings, the presence of all parts of the magnetic system and return springs; the condition of flexible connections, the presence and condition of spark arresters, the presence of a non-magnetic gasket or short-circuited turn and their condition, the presence of fastening bolts, nuts, flat and spring washers and the quality of fastening; integrity of supporting prisms or bearings; condition of the main and auxiliary contacts and their springs. In addition, they manually check: the absence of jamming of the moving system; simultaneous closing and opening of the main contacts; presence and size of failures in main and auxiliary contacts; correct operation of auxiliary contacts; density of magnetic circuits. The correct operation of the contacts and the stiffness of the springs are assessed during testing and adjustment by comparison with other contactors of this type (in case of emergency, according to catalog data). When closing and opening, one contact should slide relative to the other (rolling).
The dimensions of solutions and dips are indicated in special tables of the manufacturer. If the measured and factory data do not correspond, additional adjustment of the contacts is performed.
The insulation of contactors, coils, contactor-relay and other equipment is checked when monitoring the insulation of secondary switching circuits of the entire control circuit and power circuits of the installation. Separately, the devices are turned off only if it is necessary to find an area with low insulation.
Next, the operation of the device is tested by applying operating current to its coil. At the same time, for DC contactors, the serviceability of the coil, the correct installation of the springs, the free movement of the moving part, the correctness of the gaps are checked, and for AC contactors, the behavior of the magnetic system is checked. If the vibration of the magnetic system is significant and the armature is humming, check the alignment of the armature when turned on and the presence of distortions. In case of insufficient diligence or distortions, additional mechanical adjustment is performed, and, if necessary, grinding of the poles. Next, they control the operation of the circuit, the clarity of switching on and off the devices at rated and reduced switching voltage up to 0.9 Unom, switching off up to 0.8 Unom. on operational current busbars. If, at low voltage, the clarity of switching on the devices decreases or they do not work, check and adjust the pull-in and drop-out voltage of contactors or magnetic starters according to the diagrams shown in Fig. 2, a, b.
The most common faults of starters and contactors are:
— vibration of the magnetic circuit of AC starters and contactors, caused by the absence of a short-circuited turn, contamination of the contact planes of the electromagnets or loose contact of the surfaces of the electromagnets;
— increased heating of the coils of starters or contactors, which is explained by the low economic resistance of DC contactors and the increased gap of the middle rod of contactors and AC starters;
- burning, deep corrosion of contacts, which is explained by the fact that they are not touched at the same time, insufficient initial pressure of the contacts, or their vibration when touched.
Repair work As a result of operation, accidents, overloads and natural wear and tear, some electrical equipment and networks fail and must be repaired. Repair- this is a set of operations to restore serviceability or performance electrical devices, restoration of their resources or their components. A repair operation is understood as a completed part of a repair performed at one workplace by performers of a certain specialty, for example: cleaning, disassembling, welding, making windings, etc. In electrical devices, moving, fixed and arcing contacts are most often damaged. Repair mainly consists of identifying the malfunction, eliminating it, replacing damaged and worn parts, followed by adjustment and testing. During operation, the contacts are cleaned of metal deposits, soot, and oxides. Clean with a file with a fine (fine) notch. Eliminates strong and weak contact pressure. To do this, place paper (foil) between the contacts, pulling the movable contacts through a dynamometer and pulling out the foil. Normal force is 0.5-0.7 kg. The magnetic contact system can create noise, humming, reasons for this:
The armature does not fit tightly to the core, damage to the short-circuited turn;
Very high contact tension, the armature is skewed in relation to the core;
There is rust where the armature and core touch;
For magnetic starters and contactors, the closure of power contacts must not be allowed to close at different times.
Short-circuited turns for contactors and magnetic starters are made of copper, brass and aluminum. They fit into stamped grooves at the ends of the core. Attention is drawn to arc chutes. Their absence can cause the arc to overlap individual phases. Coils are repaired in case of frame damage, breaks, turn short circuits and complete combustion.
A break in the coil is detected if no traction force is developed and no current is consumed. A turn fault is detected by abnormal heating and decreased thrust. For contactors, main contacts, flexible connections, arc chutes, coils, springs, and short-circuited turns are often replaced. The insulation resistance of the windings should not exceed 0.5 MOhm. The heating elements of the relay burn out more often. Nichrome and fechral are used for heating elements. Individual heating elements are made by stamping. Spiral heating elements are cadmium coated to protect against oxidation. Contact repair. Contamination, wear, burning, soot or oxidation, deposits and splashes of metal on the surface of moving parts, including knife switches or fixed (knife jaws) contacts, as well as on plates and contact bridges, are eliminated with a cotton napkin soaked in gasoline or a file. If the contact springs are broken or weakened, or the anti-corrosion coating is damaged, the springs are replaced.
Repair of electromagnet coils. Reels can be framed or frameless. The most common damage is cracks up to 15mm long in the frame. They are eliminated as follows. The surface of the frame around the crack is cleaned of dust and oil with a cotton cloth soaked in gasoline. If the outer layer of the coil insulation is damaged or the winding wire breaks in the upper layers of the winding, remove the outer insulation of the winding and the damaged turns to the point of damage or breakage, solder, insulate the soldering area of the new winding wire and wind the required number of turns, repeating the operations that are performed when winding new coils . In case of significant damage to the frame, interturn short circuits, or burning of the winding insulation to a great depth, the coil must be replaced with a new one. Repair of frame reels. Select the frame and wire required for the coil, the parameters of which must correspond to the passport data. Before installation on the winding machine, the frame should be wrapped in a double layer of electrical insulating paper with a thickness of 0.02-0.03 mm and the end should be glued to the frame. When winding, you must ensure that the tension on the wire is not excessive, as this may cause the wire to break. When winding, the wire should lie in an even, dense layer. Between the 1st and 2nd layers of the winding, interlayer insulation made of insulating paper is laid. If the coil is heat-resistant, then thin fiberglass fabric is used for interlayer insulation.
Repair of magnetic circuit. Contaminants are removed with a cotton cloth soaked in gasoline; traces of corrosion are thoroughly cleaned with a steel brush and sandpaper; hardening on the contact surfaces of the core and yoke is removed by grinding the surface with a file on a grinding machine.
OCCUPATIONAL SAFETY
Organizational measures Organizational measures to ensure safe work in electrical installations are:
a) registration of work with an approval order, order or list of work performed in the order of current operation;
b) permission to work;
c) supervision during work;
d) registration of a break in work, transfers to another workplace, finishing work.
Order, order, current operation
Work in electrical installations is carried out according to orders, orders, and in the order of routine operation. Outfit- this is a task for the production of work, drawn up on a special form of the established form and defining the content, place of work, time of its beginning and end, conditions for safe performance, composition of the team and persons responsible for the safety of the work, etc. Along with this, work can be carried out in electrical installations performed:
a) with stress relief;
b) without relieving voltage on live parts and near them.
Order- this is an assignment for the production of work, defining its content, place, time, safety measures (if required) and the persons entrusted with its implementation. The order can be transmitted directly or using means of communication with subsequent entry in the operational journal. Current operation is the carrying out by operational (operational and repair) personnel independently in the area assigned to them during one shift of work according to the list Persons responsible for the safety of work, their rights and responsibilities Responsible for the safety of work are:
a) the person issuing the order, giving the order;
b) admitting person - a responsible person from the operational staff;
c) responsible work manager
d) work performer;
d) observer;
f) team members.
The person issuing the order, issuing the order, establishes the need and scope of the work, is responsible for the possibility of its safe execution, the sufficiency of the qualifications of the responsible manager, the work performer or supervisor, as well as the team members. The right to issue orders and orders is granted to persons from the electrical technical personnel of the enterprise authorized to do so by order of the person responsible for the electrical equipment of the enterprise. These persons must have an electrical safety group of not lower than V in electrical installations with voltages above 1000 V and not lower than IV in installations with voltages up to 1000 V. The right to give orders for the performance of a number of works, the list of which is determined by the person responsible for the electrical equipment of the enterprise, is also granted to persons from the operational personnel with a group not lower than IV.
Permissive- the responsible person from the operational staff is responsible for:
a) for the correct implementation of the safety measures necessary for admission and performance of work, their sufficiency and compliance with the nature and place of work;
b) for correct admission to work, acceptance of the workplace upon completion of work with registration in orders or magazines.
The permittee must have an electrical safety group of at least IV when working in electrical installations above 1000 V and at least III in installations up to 1000 V.
Responsible manager, accepting the workplace from the permitting person and making admission, is responsible, along with the permitting person, for the correct preparation of the workplace and the sufficiency of the safety measures taken necessary for the work, including the sufficiency of the measures provided for in the work order column. Separate instructions The responsible manager is prohibited from taking direct part in work on orders, except in cases where he combines the duties of a responsible manager and a work producer. Responsible managers are appointed persons from the electrical personnel who have electrical safety group V.
Producer of works, accepting the workplace from the person admitting it, is responsible for the correctness of its preparation and for the implementation of the safety measures necessary for the work. The work manager is obliged to instruct the team about the safety measures that must be observed during work and to ensure their implementation by team members. The work performer complies with these Rules himself and is responsible for their compliance by team members, monitors the serviceability of tools, rigging and other repair equipment. The work performer is also obliged to ensure that the fences, posters, and groundings installed at the work site are not removed or rearranged. The manufacturer of work performed on electrical installations with voltages above 1000 V must have an electrical safety group of at least IV, in installations up to 1000 V - group of at least III. The manufacturer of work carried out by order in all electrical installations must have a group of at least III
Watching appointed to supervise teams of construction workers, general workers, riggers and other non-electrical personnel when they perform work in electrical installations according to orders or orders. A supervisor of electrical personnel, including seconded personnel, is appointed in the event of work being carried out in electrical installations under particularly hazardous conditions, determined by the person responsible for the electrical equipment of the enterprise where this work is being carried out. The observer controls the presence of groundings, fences, posters, locking devices installed at the work site and is responsible for the safety of team members from injury electric shock electrical installations. The supervisor is prohibited from combining supervision with the performance of any work and leaving the team unsupervised during work. Persons with a group of at least III are appointed as observers. Team members are required to comply with these Rules and instructions received upon admission to work during work.
Technical events. To prepare the workplace when working with stress relief, the following technical measures must be carried out in the specified order:
a) the necessary shutdowns have been made and measures have been taken to prevent the supply of voltage to the place of work due to erroneous or spontaneous switching on of the switching equipment;
b) on manual drives and on keys remote control prohibiting posters were posted on switching equipment;
c) checked that there is no voltage on live parts that must be grounded to protect people from electric shock;
d) grounding is applied (grounding blades are turned on, and where they are absent, portable grounding connections are installed;
e) warning and ordering posters are posted, workplaces and remaining live parts are fenced, if necessary.
When performing operational maintenance of an electrical installation by two or more persons per shift, the activities listed in this paragraph must be carried out by two people. In the case of individual maintenance, they can be performed by one person, except for the application of portable grounding in electrical installations above 1000 V and switching carried out at two or more connections in electrical installations with voltages above 1000 V, which do not have operating devices for blocking disconnectors from incorrect actions