The equipment is often subjected to overload and mechanical damage. It is only worth dropping or shedding something on the tool, as rust appears on the winding of the rotor, and the anchor itself moves. The consequences are deplorable: the electric motor overheats, sparks and vibrates. Working with such a tool is dangerous.
If you have the skills to repair equipment and a minimum set of tools, then rewinding the anchor at home will help to fix the problem. The fact is that it is the winding that takes on the first “blows” of improper operation. The wires of the conductor are torn and burned. Their replacement will extend the life of the equipment and increase engine performance.
How to rewind the motor anchor at home
Before starting repairs, prepare tools and materials:
- multimeter. If it is not, then you will need a voltage indicator, a megger and a 12 V bulb with a power of 30–40 W,
- new winding. The diameter of the core must be identical to the diameter of the old winding,
- soldering iron
- dielectric cardboard 0.3 mm thick,
- varnish or epoxy resin
- a skein of thick cotton threads,
- sand paper.
In order not to do unnecessary work, it is important to correctly identify the cause of the breakdown of the equipment. To do this, inspect the tool and check whether current is flowing to the collector and start button using a multimeter or indicator. If everything is in order, then you need to inspect the device from the inside.
Disconnect the tool from the power, and disassemble the case. Smell the rotor. If an interturn circuit occurs, the insulation coating is melted and exudes a pungent odor.
When there are no external signs of malfunction, it is worth checking the lamellas of the anchor with a multimeter. Switch the instrument to ohmmeter mode and set the range to 200 ohms. With two probes "ring" adjacent lamellas. A change in resistance indicates a breakdown in the coil.
An ohmmeter can be replaced with a light bulb. Connect the plus and minus terminals to the plug of the device, and put the lamp in the gap. Turn the armature shaft by hand. If the light “blinks”, then an interturn circuit has occurred. Is the lamp off? So, an open circuit has occurred or there is no resistance in one of the lamellas.
Winding replacement and new insulation will prevent motor burnout. To extend the life of the electric motor, it is recommended to rewind the rotor at least once every two years.
Instructions: how to rewind the armature winding
Before rewinding, you need to fix the main indicators of the engine. Count and write down: the number of grooves of the anchor and lamellas of the collector. Determine the winding pitch. The most common step 1–6 is when the coil is placed in the initial groove, then in 7 and fixed to 1 groove.
In some factory windings, a reset to the right or left is applied. For example, when winding and resetting to the right, the coil goes to the right of the initial groove. So, with the number of grooves of the anchor 12, the winding step 1–6 and the discharge to the right, the winding is laid in 1 groove, then in 8 and after winding the desired number of turns, it is fixed in 2 groove. All this must be taken into account. Otherwise, the winding will be laid incorrectly, which will negatively affect the direction of rotation.
Rewinding the armature of the electric motor with your own hands will take about 4 hours. In order to avoid difficulties during assembly, it is recommended to photograph the initial location of the parts during each stage of work:
- Determination of the direction and initial groove of the winder. Find a coil on the winding that is not blocked by others. This is the last reel. If the winding is laid to the right, it means that the initial groove is located to the right of the left side of the last coil. With it, you need to start laying the conductor. So the rewind of the anchor will be as close as possible to the factory conditions. Mark the groove with a marker. With the initial symmetric winding, the coils are stacked in pairs, so the last coils and the initial grooves are also two. Get them out too. To find the grooves without any difficulties, pay attention to the image:
- Counting turns. It is necessary to determine the number of turns in the groove (W) and in the coil of the winding (K). Separate the top coil and count the turns. If necessary, the coil is fired in the flame of the burner. The nuance of the calculation is that the number of turns of a single coil in a groove depends on the ratio of the number of collector lamellas to the number of anchor grooves. For example, in the last coil there are 60 turns (W), in the anchor there are 12 grooves, and the collector lamellas are 36. Then the value of K will be 10 (60 6), where 6 is the ratio of grooves to lamellas multiplied by 2.
- Collector preparation. You do not need to remove it. Measure resistance between lamellas and the case. To do this, use a megger or put the multimeter in the appropriate mode. The minimum resistance is 200 kΩ, the maximum is 0.25 MΩ.
- Dismantling the old conductor. Carefully, without damaging the armature body, remove the old winding.
- Cleaning the grooves and the anchor body. All deposits and burrs must be sanded with sandpaper.
- Production of sleeves for an anchor. From dielectric cardboard, cut the rectangles in accordance with the size of the grooves of the anchor.
- Rewind Carefully review all notes made in preparation for the repair. Do-it-yourself anchor rewinding scheme must fully correspond to the factory one. The end of the new winding is soldered to the end of the lamella. The wire must be laid from the initial groove, observing the pitch and discharge of the winding.
- Fastening. Wrap a few turns of cotton thread tightly around the winding near the collector to secure the coils. Synthetic threads cannot be used - they are melted.
- Circuit Testing. As with diagnostics, check the winding for breaks and inter-turn short circuits.
- Treatment. If the check does not reveal any malfunctions, then cover the winding with varnish or epoxy resin and dry. To speed up the process, you can send the anchor to a conventional oven for 20 hours at a temperature of 80 degrees.
Rewind is complete. With some skill, repair does not take much time. If you changed the winding for the first time, and are not completely sure of the correctness of the wire laying, then you can conduct an additional check.
Do-it-yourself static balancing of the motor armature
The key to the smooth operation of the equipment after rewinding the anchor is proper balancing. In large companies for the repair of electric motors, dynamic balancing is done on a special machine. Since it is difficult to rewind the anchor for the first time it’s difficult to identify gross errors, the device for static balancing “On Knives” will help. It is easy to construct it yourself.
Pick up two steel blades. They should have good straightness and purity of processing. Place the blades on a rigid base parallel to each other. The distance between the blades is the size of the anchor. The result should be such a device:
Schematic representation of the device "On the Knives", where 1 is the motor anchor, 2 are steel blades, 3 is the base, A and B are points for soldering loads.
The balancing method is simple: the anchor is placed on the blades and observe its movement. The anchor will turn, as the heaviest part will be at the bottom. The task is to move the center of gravity as close as possible to the axis of the anchor, which is indicated by a dotted line. With good balancing, the anchor remains motionless. To balance the weight, plasticine weights are hung on points A and B. When equilibrium is reached, the loads are removed, weighed and brazed to a metal equal to their weight.
Now you know how to rewind the anchor with your own hands. Thanks to balancing skills, your tool will not vibrate and overheat, even with minor flaws in laying the winding. Regular contact checks and scheduled cleaning of the housing will help minimize the likelihood of equipment breakdowns.
The balancing method is simple: the anchor is placed on the blades and observe its movement. The anchor will turn, as the heaviest part will be at the bottom. The task is to move the center of gravity as close as possible to the axis of the anchor, which is indicated by a dotted line. With good balancing, the anchor remains motionless. To equalize the weight, points A and B are hung from plasticine. When equilibrium is reached, the loads are removed, weighed and brazed to a metal equal to their weight.
Now you know how to rewind the anchor with your own hands. Thanks to balancing skills, your tool will not vibrate and overheat, even with minor flaws in laying the winding. Regular contact checks and scheduled cleaning of the housing will help minimize the likelihood of equipment breakdowns.
The device of asynchronous electric motors, as well as their connection and verification were described in previous articles of this site in the section on electric motors. Very briefly need to be reminded:
- Between the terminals of the windings and the housing, the resistance should be as large as possible,
- for three-phase asynchronous motors, the resistance of all windings should be the same,
- for single-phase asynchronous motors, the resistance of the working winding should be less than that of the starting one.
The exact parameters of the winding resistances must be found out from a paper passport of the electric motor, from the Internet or from reference books. Since windings of asynchronous electric motors with a power of several kilowatts are very low (within a dozen Ohms or less), it will be extremely difficult to identify differences when testing windings using conventional digital or arrow multimeters. Therefore, use the method with an additional voltage source and a rheostat.
Measurement of winding resistance using a voltage source, rheostat and voltmeter
The place of the inter-turn circuit in the windings of an induction motor can be found by connecting a horizontally placed stator without a rotor to a reduced three-phase voltage and placing a steel ball inside. The rotating electromagnetic field of serviceable windings will drive the ball around the inner circumference of the stator. If somewhere in the windings there is an interturn circuit, then in this place the ball will be magnetized.
Installing the ball inside the stator to search for inter-turn circuit
Sometimes factory defects occur during soldering or welding, leading to a break in the connection of the terminals of the stator windings in an easily accessible place, which makes repair of the electric motor quite simple. But most often the inter-turn circuit or winding break occurs in the grooves of the stator, which requires full rewinding of the electric motor. Winding An asynchronous motor is complex and requires identical winding wires, skills and tools.
Rewinding stator windings of a powerful electric motor in a workshop
Therefore, if there is an asynchronous electric motor with obvious signs of a winding break or inter-turn short circuit, without the presence of equipment, wires and skills for rewinding, it makes sense to disassemble the case if this simplifies the work of a specialized craftsman and reduces the total cost of repairs. The stator itself without a rotor and end caps is approximately twice lighter than the entire electric motor, which can also be important when transporting to the repair site.
Disassembled induction motor
Having disconnected the electric motor, it is possible to start dismantling it manually or with the help of a lifting device. To do this, unscrew the mounting bolts and disconnect the motor shaft from the driven mechanism. Depending on the purpose, a pulley, gear, or worm gear can be tightly mounted on the motor shaft, a special tool is used to remove them - a puller. At the end in the center of the motor shaft, a recess is provided for the threaded pin of the puller.
When disassembling the motor, a lifting device may be required.
As a rule, the puller has three hooks, which you need to grab the pulley or gear to be removed, scrolling the threaded pin against the shaft by hand, achieving a tight grip. Then you need to fix the motor shaft with a pipe wrench, turning the screw with the lever. A tightly set pulley should come off the shaft in small jerks, accompanied by a characteristic creaking.
It is not recommended to hold the puller with your hands, clutching at its hooks - from the applied force of counteracting the force that tightens the stop screw, the grips can fly off, causing injury.
After releasing the shaft of the induction motor, you need to remove its rear protective cover and dismantle the fan by loosening the screw. If the fan wheel is sitting tight on the shaft, it can also be removed using a puller. Then you can remove the end caps of the electric motor, which center the rotor, so they are pressed into the groove in the stator housing.
Dismantling the motor housing and stator inspection
It is recommended that the end (frontal) covers also be removed with a puller, as they are tightly seated on the bearings. But, if there is no puller, or it does not fit, then they use the "folk" method, inserting a powerful screwdriver into the groove from different sides, prying the cover. Substituting a screwdriver at an angle, hit it with a hammer. It is necessary to strike evenly from different sides of the lid so that there are no distortions. Need to work CautionIn order not to break the cover, not to damage the windings inside, and not to be crippled.
After removing the cover, a breakdown of the stator winding was immediately detected
Remove the end cover only from the front side, since the rotor with the back cover will easily come out of the stator. Failures in a squirrel-cage rotor are extremely rare, so it can be put aside by taking up the stator windings. Already with one glance at the windings, you can understand the essence of the problem - if all, or part of the wires are blackened, then you will need to rewind the stator of the electric motor. In the absence of blackening on the wires, if an ohmmeter detects a break, you should carefully examine the connection points of the windings.
Part of the windings turned black from overheating - this stator needs rewinding
The connections of the windings of an induction motor can be invisible at first glance, since they are insulated and fixed with a brace. It will be necessary to study the connection diagram of the windings, since in asynchronous motors they are connected in different ways, depending on the number of poles, on which the speed of the electric motor depends. Having studied the structure of a specific model of an induction motor, and having found all the connections of the windings, you need to make sure that they have reliable contact.
Stages of rewinding an induction motor
As a rule, at this stage of repair of asynchronous motors, most home masters stop and turn to specialists. But, many enthusiasts continue to repair, and try to rewind the motor windings on their own. The concept of “rewinding” does not accurately reflect the essence of the process - first remove the old winding wires, then wind coils from the new conductors on the winding device, after which the coiled turns of the updated winding are placed in the stator slots.
After disassembling the motor, an interturn circuit in the windings was detected - rewinding is required
Removing old stator windings
To remove old windings, first you need to cut with a knife all the binding ropes and adhesive fasteners, clean the wires from soot and dirt, without breaking the electrical connections, from which you also need to remove the insulation. Then you need to photograph the connection of the terminals of the electric motor and the stator windings on both sides, so that later you can repeat the connections exactly. You will also need to draw up a winding connection diagram, or find out from the directory.
Take pictures of winding connections
Using a suitable punch, wooden (or textolite) pegs are knocked out of the grooves of the stator magnetic circuit. Having dismantled all the pegs, remove the insulating gaskets, exposing the wires of the windings that are glued together with varnish. Find the outermost wire from the junction and pull it toward the center of the stator, peeling off the rest of the winding. Then take the next turn, and also release, one after another, until the entire groove is released until the insulating strip.
Stator of an induction motor freed from windings
Then release the next groove, moving in a circle. Thus, it is possible to understand the principle of winding the windings, and more importantly, to photograph their location and connection, so that later they can place the new windings in the right order, and use the burnt wire as a fixing wire in the household. Manual unwinding of the windings will be useful to a beginner, although experienced winders cut with a chisel the wires at the ends of the stator are much faster.
Cutting windings with a hammer and chisel
Winding and laying of stator windings
When unwinding the windings, it is necessary to remember the number of turns in each winding, as well as measure the length and width of the resulting coil. Затем нужно приобрести обмоточный медный провод с идентичным поперечным сечением и необходимыми электротехническими характеристиками изоляции.
Катушки намоточного провода для перемотки электродвигателей
There are a lot of training videos on the Internet on self-winding stator windings of an asynchronous electric motor, but for the first time, the advice and tips of an experienced master rewind electric motors will also be useful.
Before the repair of the electric motor, its fault is carried out - a term meaning the search for defects, cracks, flaws in various parts of the motor. Regarding the rewinding of the stator windings, defect means the search for scratches and dents in a lined magnetic circuit whose closed plates degrade the general characteristics of the electric motor. Rewind masters also call defect selection of winding parameters according to the dimensions of the stator.
Carefully inspect the stator for defects and damage.
Groove and wire preparation
New insulating gaskets are inserted into the grooves of the stator - this process is called sleeving. Gaskets are cut out of special electrical insulating material. The required thickness, heat resistance and dielectric strength of the insulating material is determined by reference, knowing the parameters of the repaired asynchronous electric motor.
Insulation pads are installed in the grooves of the stator
The next stage of the master is called the fault detection of the parameters of the winding of the induction motor - according to the dimensions of the stator, based on the tables of special reference books, the parameters of the winding wire and the number of turns are determined. If the number of turns of each winding group (coil) has been calculated earlier, and the necessary directory is not at hand, this step can be skipped, hoping for its thoroughness.
An example of a reference for the wizard for rewinding induction motors
Next, the coil groups are wound with a special insulated copper wire, which is supplied in coils. When purchasing a winding wire, you need to make sure of the quality of the insulating coating and the compliance of the diameter with the value specified in the documents. Check the thickness of the wire with a micrometer or wrap a certain number of turns on the pencil closely and measure in millimeters the length of the formed coil. Dividing the length of the coil by the number of turns, get the diameter of the wire.
Winding and laying the windings in the grooves of the stator of the electric motor
In workshops, the winding of coil groups (loose windings) is carried out by a special winding machine, in which there is a counter for counting turns and extendable oblong pads of various sizes to give the coils the desired shape. At home, from a suitable material, they make a block for a winder with previously measured dimensions or in accordance with the parameters of the coil from the directory.
Having set the drum on an axis with a lever, wrap the required number of turns of each reel group - it is very important not to make a mistake in the score. After winding the required number of turns, the wires are temporarily tied so that they do not fray
Coil groups are laid on a table with a soft coating so as not to accidentally scratch the insulating varnish of the formed coils. Passing the coil into the stator, cut the temporary bandage and lay the windings in the grooves, prying the wires in turn through a narrow gap. The winding wires are guided by a wooden device in the form of a blunt knife. Having laid the coil group in the groove of the stator, it is tied, a gasket is inserted and fixed, driving a special peg from the end of the stator along the entire length of the groove. Then go to the next reel group, according to the winding pattern.
Bandage and connection of windings
After laying the windings in all the grooves, special inter-coil insulators are inserted between the coils in the form of strips of insulating material, then they begin to bundle the coil groups. At first, a strapping (bandage) is made from the stator back with a special rope, passing it through the loop of the windings by a hook, tightening the wires and inter-coil insulators, trying to prevent the insulating material from slipping out of the set place.
Insulating material between windings
After laying the windings, many conclusions of the coil groups will stick out from the front of the stator, which are connected according to the connection diagram or the photograph taken identically earlier. At this stage, it is very important not to confuse the conclusions of the already laid winding coils, so the wires are bent radially and connected by twisting for subsequent welding. When soldering joints, there is a risk of solder melting and contact loss from vibration.
An example of a connection scheme for windings of an asynchronous three-phase electric motor
After connecting all the coil groups of the winding, you can check the correct connection by measuring the resistance at the terminals and the breakdown on the housing. After checking, the stator of the electric motor is heated to the desired temperature (about 50ºC) and impregnated with a special varnish by the method of complete immersion. With this method of impregnation, the varnish penetrates into all the grooves and voids, providing mechanical strength of the windings and additional dielectric insulation.
Rewound stator dipped in hot varnish
Checking windings and motor assembly
After impregnation, the stators are installed in drying chambers for drying for several hours at temperatures up to 130ºC. In the process of drying the varnish, the windings, the insulating material and the bandage become a single strong elastic structure, resistant to the effects of moisture, dust and mechanical stress.
Motor stator after rewinding
After the engine cools down, the final winding test megger and ohmmeter, checking the dielectric strength of the insulation (breakdown) and the integrity of the windings. The resistance of the windings of a three-phase induction motor must coincide with a tolerance of 0.3 Ohms for a small electric motor with a power of 1-3 kW.
The motor leads are output to the terminal strip and connected to the terminals. Insert the rotor and press on the covers, fixing them with screws. The final test is to test the asynchronous motor with mains voltage for several minutes. Smooth and monotonous humming of a working electric motor, as well as the same current in all three phases, will indicate the correctness of the rewinding of the induction motor.
Causes and signs of stator failure
Manual grinders, popularly called “grinders”, can fail for various reasons. The most common problem is the breakage of the stator turns, which occurs due to an excessively strong load on the device. Now, such a malfunction can be corrected independently - correctly rewind the stator.
There are frequent cases when the failure of the electrical part of the device becomes the cause of the breakdown. Various factors lead to this:
- water entering the surface through which the current flows,
- power surges,
- sharp pulling out the plug from the outlet,
- high overloads and, as a result, overheating.
There is an opinion that it is impossible to rewind the stator yourself. In fact, it’s enough to understand the design of the device. If you have experience with such work and the necessary knowledge, you can repair a three-phase start-up device at home. Given the preparatory work, the process can take several hours.
Often the engine fails due to a break in the magnetic circuit, violation of the winding or anchor. With increasing voltage, an abrupt increase in the strength of the spark is noted. Usually this is observed on only one brush. This phenomenon leads to the destruction of the insulation of the wires on the stator coil. If, when turned on, the drive accelerates very quickly and gains momentum, this indicates a stator short circuit.
Sparks that occur during the operation of the collector signal the occurrence of violations in the balancing of the armature. Checking the operation of the collector can be done in this way: when turned on, the sound should amplify gradually with increasing voltage. No vibrations should occur. If there is resonance, the Bulgarian electric motor needs repair.
The grinding tool consists of three important components:
The anchor is a rotating element with a winding and creates the torque of the electric motor. On the stator, divided into sectors, there is the same winding. The current through the carbon brush passes through the winding, enters the anchor. Then the current passes to other brushes until all parts of the stator are involved. When electric current passes through the winding, a magnetic field constantly interacting with the stator arises. Thus, an electric motor is driven. There are several characteristic breakdowns of the launch device "grinder":
- burning or rupture of the winding,
- a short circuit between the turns of the winding,
- destruction of insulation.
You can rewind the winding with your own hands, without contacting a specialist. You only need to disassemble the device first. But if you are not completely confident in your abilities, then contacting a specialized workshop will be the most reasonable step. First of all, the casing shifts. To do this, the screw fixing it is unscrewed. After that, it will be possible to see all the details of the grinder, except for the gearbox hidden under the metal cap. The screws that secure the metal plate are loosened. Now all the mechanical parts are clearly visible. Only after this can you move on to rewind the stator.
Better than a well-made repair can only be the correct operation, in which there will be no breakdowns at all. In order for the “grinder” to work longer, the following simple rules must be observed:
- In no case should you exceed the amount of grease and the timing of its addition or replacement.
- After the tool has been operating at reduced speed, it is strictly forbidden to immediately turn it off. If you leave it to work for at least 1 minute, you can avoid overheating.
- Do not allow long-term operation of the tool at reduced speeds under load.
A refurbished stator will allow the grinder to operate normally for a long time.
Repair preparations and necessary tools
To rewind the stator, you will need special tools:
- hammers: wooden, metal,
- pliers and pliers
- steel brush
- electric drill,
The first and most important stage is the cleaning of the stator from contamination. The old winding is removed from the grooves. All this can be done with a steel brush. Cleaning is carried out manually using steel brushes, electric drills. It is also necessary to remove the old insulation. To facilitate the task, transformer oil can be used. It is necessary to warm it a little and lower the launch device into it. Such a measure will soften the damaged insulation and simplify its removal. For cleaning, a mild caustic solution (temperature - 80ºС) mixed with compressed air is also used.
After treatment, the stator should be washed well with water and dried. The condition of the stator and steel bags must be well checked. Then pull the studs tightening the core, the grooves are cleaned from burrs. Insulation resistance is measured with a megger. Parts of the core, thrust washers and grooves are varnished. Washers and slots must be insulated.
The accompanying note, where the main data is displayed, can facilitate further work:
- phase connection diagram and their number,
- coil and phase resistance
- number of grooves and their sizes,
- winding cross-section, pitch of coils in grooves,
- The method of isolating the groove, the number of interlayer gaskets and their sizes.
Stator Rewind Stages
When working, it is important to get a strictly defined number of turns - it should be identical to the number of turns of the old winding. The wire must be wound so that the seal is maximized. Coils are placed in the stator. From the same material from which the winding for the coils is made, conclusions are drawn. Their tips need to be insulated with cambric - tubes made of plastic.
Before installing the coils, it is necessary to check that the groove boxes are symmetrical. They must close the winding. If this does not happen, when inserting the wires of the coils, temporary inserts are placed. This simple measure will avoid damage.
The coil is mounted above the groove, which is located below the bore. Coil conductors are installed using a special plate. The wires located in the groove should never cross over. They need to be laid in the same way, in the same sequence as the winding. Conductors must be installed strictly in parallel.
To perform the next operation, the stator needs to be slightly rotated - only one division. Coils from the same group fit into the groove. After laying, lay the interlayer gaskets. Screw the terminals onto the external circuit so that they are parallel to the external circuit. The underside of the coils is mounted in the same way. The operation is repeated until the grooves of this step are full.
When the winding is finished, the ends can be plugged. The dimensions of the sleeves depend on the size of the stator. The thickness of the sleeve is usually 0.2 mm, but the length should be greater than the size of the launcher. Most often, this value is about 1.5 mm. For the manufacture of liners using special cardboard. A film must be wound on it (it must be heat-resistant). The whole structure is wrapped with tape. Coils with sleeves must be installed in the grooves of the stator. After that, you can check whether the anchor is moving correctly. The coil is completely ready. It remains only to wrap with kiper tape, and on top to cover with a layer of varnish. After the varnish has dried, the device is completely ready for use.
In everyday life and small workshops, electric motors are used. Sometimes they fail . Determine whether they can be repaired on their own, or if you need to contact the master, this article will help. Malfunctions of electric motors can be divided into two groups - mechanical, for example, a seized bearing or a broken shaft and electric - mechanical breakage of the winding or its failure due to overheating of the electric motor.
Malfunctions of electric motors
The reasons for overheating of the electric motor can be many, but the main reason is this is incorrectly selected protection against overcurrent or its complete absence.
Electric motors used in everyday life can be divided into two groups
- squirrel-cage or phase-locked asynchronous automobile generators
- AC and DC collector motors
Each type of electric motor has its own characteristics when rewinding burned windings.
Squirrel Cage or Phase Rotor Induction Motors
Before repair, the electric motor must be cleaned with a rag of dust and dirt. The cleaned engine is subjected complete disassembly . Before replacing the windings, the pulley or clutch located on the front shaft of the electric motor can not be removed, but the condition of the front bearing cannot be assessed with them. Worn out motor bearings may be cause engine failure .
In the absence of burned spots and a characteristic odor, the windings are disconnected from each other and the isolation with respect to each other and the housing is called with a megger and the integrity is checked by a tester. If the insulation is not damaged, and the tester shows a break, then you can try to find the break and fix the problem without rewinding. Often a wire breaks out of the engine. In this case, it can be re-soldered or replaced.
In the absence of breaks and integral insulation, a possible malfunction is interturn circuit . In three-phase electric motors connected to a three-phase network, this is verified quite simply. It is necessary to measure the current at all phases alternately with current clamps or an ammeter, or, if possible, at the same time. The difference in values of 2-3 times clearly indicates the interturn closure and the need for rewinding. By the same methods, the rotor is checked in electric motors with a phase rotor.
In single-phase or three-phase, but connected to a single-phase network motors, a round circuit is indicated by strong heating when turned on without load, provided there are no breaks, insulation failures, mechanical malfunctions of the engine and starting equipment. For example, a single-phase motor on old washing machines is heated with the starting winding constantly on.
If a decision is made to rewind the electric motor, it is best to contact for repair to a specialized workshop . In "home" conditions it is very difficult to perform this work in a high-quality manner, which can lead to its quick failure. But if there is a need or desire to repair the electric motor with your own hands, then in youtube, for the query “rewind electric motors with your own hands”, you can find videos with detailed instructions.
The rewinding process can be divided into three stages
It is necessary to continue disassembling and removing the windings - completely or, if the design allows, only damaged ones, to rewind them only. Перед полным удалением разрезают нитки, связывающие провода вместе и зарисовывают схему соединения. Проще всего удалить старые обмотки путём выжигания газовой горелкой или на костре. Можно поставить статор «на попа» на кирпичи, заполнить дровами и поджечь.
Снять обмотки можно также с помощью зубила и молотка, но в этом случае труднее определить схему подключения and the order of laying the windings in the grooves.
In single-phase motors, it is sometimes possible to remove one winding without touching the others. In this case, you need to carefully consider how the windings are attached and remove the damaged one.
The phase rotor is disassembled similarly, but before burning out, it is necessary to remove the slip rings.
Scorched windings are carefully removed from the grooves, trying to keep at least one intact. This is necessary to determine the size of the winding, the cross-section of the wire and the number of turns. When disassembling, they also sketch styling scheme windings in grooves indicating the direction of winding. If the type of electric motor is known, data for repair can be found in the corresponding directories.
Knowing the number of windings, the size of each and the number of turns by multiplying, you can determine the desired length of the wire. The wire cross section is taken the same as on a burned-out one. It is measured with a caliper or micrometer. If the cross section is taken less, then the engine will overheat at rated loads, and if it is larger, then the wire may not fit in its grooves.
Winding is carried out on a machine similar to those machines on which the transformer coils are wound. After winding the desired number of turns, the winding is removed from the machine, tied with a winding thread and laid aside. Process repeats as many times as necessary windings.
New gaskets made of insulating material are inserted into the grooves. These gaskets are called "liners." Thickness and material can be determined by reference. If there is no data on the rewinding motor, it can be taken at a similar power. The length is taken a few millimeters longer than the thickness of the stator, the width is such as to completely cover the inner surface of the groove.
According to the scheme, they are placed in the grooves of the winding, observing the direction of the winding. If two windings fit into one groove, and also strips of insulating material are laid in the places of contact.
To lay the wire in the grooves, a special tool is used - tamper. Stacked windings are fixed with gaskets from the same material from which the sleeves were made. These pads are called “arrows”. The length of the arrows is equal to the length of the liners, and the width is half smaller.
The fixed windings are interconnected by twists that are soldered. To those conclusions on which voltage will be supplied, wires of the corresponding section and length are connected. They must be marked indicating the beginning and end.
The connected windings are tied with a winding thread or twine. The wires are led out through an opening in the stator housing and connected to the terminal block.
The rewound stator is impregnated with varnish. To do this, it is completely immersed in varnish, followed by drying. The temperature of the impregnation and drying depends on the varnish used and are indicated in the instructions.
The phase rotor is rewound similarly, only slip rings are worn on the motor shaft, to which the wires are connected.
Assembled and dried engine can be assembled. Before assembling, check the bearings and, if necessary, change the grease or the bearings themselves. After assembly, the motor is checked for insulation integrity and operability in idle mode and under load, with current measurement at all phases.
AC and DC Brush Motors
First of all, the malfunction is visible by increased sparking on the collector and heating. First you need to clean and, if necessary, grind and drain the collector. If this does not help, then with an ohmmeter it is necessary to sequentially measure the resistance in series between all adjacent collector plates. If the values are significantly different from each other, then the collector or coil in the armature windings (in the AC motor - rotor) is out of order. In this case, the engine must be given for repairs to a specialized organization . It is almost impossible to repair it at home.
In the event that the armature is intact, the field windings are checked for integrity by an ohmmeter and a loop circuit. To do this, they are connected in series, if necessary, shorting the brushes or stripping the insulation on the connecting wires. A low voltage of 12–36 v is applied to the connected windings. The voltage on the damaged winding will be significantly reduced. It is replaced in the same way as in single-phase low-power motors.
Rewinding an asynchronous motor winding to a Slavyanka hybrid winding
When rewinding a brushless motor, it can be rewound using the Slav technology. The method consists in winding with a thin wire additional stator windings. Engines wound by this method have an increased starting and operating torque, overload capacity and efficiency, reduced starting current and noise level. Due to the "soft" load characteristics, they are used on electric vehicles.
The principle of rewinding
After disassembling the tool, it is necessary to carefully assess the condition of the collector. You will need to clean it from the traces of the old rubble. In addition, before replacing the motor winding, do not discard the old one.
It is worth remembering that the winding has very obvious characteristics. It is about what needs to be measured:
- coil length
- wire cross section
- the number of turns per groove, etc.
Based on the data obtained, it will be possible to repeat the winding of the tool on its own, which has become unusable. Do not forget that before you pull out the old winding, it will need to be burned.
The return winding which is in the collector must be measured. Implied measurement of resistance. If it exceeds 0.2 Ohms, then it will have to be replaced.
In this case, the repair becomes unjustified. It will be more efficient to purchase a new tool. Moreover, it is more effective not only in time but also in money.
Rewinding Anchors: Key Points
At the very beginning, it is necessary to cut small strips from specialized electrical cardboard. They will be used for the production of thermowells. The bottom line is that the indicated strips will be inserted into the grooves of the anchor.
Only after this can you start laying the winding.
Laying the winding in the grooves should be carried out progressively. An error of one revolution can fatally affect the technical characteristics of a rewound motor. Without fail, before sending the anchor to varnish impregnation, it is necessary to check the winding with the help of a tester.
To do this before impregnation will be much easier. In addition, fixing flaws is not difficult.
- Learn how to connect a three-phase motor in a single-phase household circuit.
- Do you know what a classic asynchronous motor is - http://euroelectrica.ru/chto-takoe-asinhronnyiy-elektrodvigatel/?
The video demonstrates the professional rewinding of the stator of an electric motor: