In many home appliances and makeshift designs used as a drive electric cars small power. Despite the high reliability of electric motors, their failure for a number of reasons is not uncommon. Given the relatively high cost of these devices, it is more practical to repair them rather than replace them. We suggest considering the possibility of rewinding electric motors at home.
Types of electric motors and features of their repair
As a rule, collector motors are used in everyday life. direct current and brushless asynchronous motors alternating current. It is the repair of these drives that we will consider. Information about the principle of operation and design features of asynchronous and commutator machines can be found on our website.
As for synchronous drives, they are practically not used in everyday life, therefore this topic is not covered in this publication.
Features of the repair of an asynchronous machine
Problems with any type of engine can be mechanical or electrical in nature. In the first case, strong vibration and characteristic noise may indicate a malfunction, as a rule, this indicates problems with the bearing (usually in the end cap). If the malfunction is not eliminated in time, the shaft may jam, which will inevitably lead to failure of the stator windings. Wherein thermal protection circuit breaker may fail to operate.
Based on practice, in 90% of the failure of asynchronous machines there are problems with the stator winding (open circuit, interturn short circuit, short circuit to the case). In this case, the short-circuited anchor, as a rule, remains in working condition. Therefore, even with the mechanical nature of the damage, it is necessary to check the electrical part.
Winding check
In most cases, the problem can be detected by appearance and characteristic odor (see Fig. 1). If the malfunction cannot be established empirically, we proceed to diagnostics, which begins with a continuity call for an open. If one is found, the engine is disassembled (this process will be described separately) and a thorough inspection of the connections is performed. When a defect is not detected, it is possible to ascertain a break in one of the coils, which requires rewinding.
If the continuity did not show a break, you should proceed to measuring the resistance of the windings, while taking into account the following nuances:
- the insulation resistance of the coils to the housing should tend to infinity;
- for a three-phase drive, the windings must show the same resistance;
- for single-phase machines, the resistance of the starting coils exceeds the readings of the working windings.
In addition, it should be borne in mind that the resistance of the stator coils is quite low, so it makes no sense to use devices with a low accuracy class to measure it, such as most multimeters. You can correct the situation by assembling a simple circuit on a potentiometer with the addition of an additional power source, such as a car battery.
The measurement procedure is as follows:
- The drive coil is connected to the circuit shown above.
- The potentiometer sets the current to 1 A.
- The coil resistance is calculated according to the following formula: , where R K and U PIT were described in Figure 2. R is the resistance of the potentiometer, is the voltage drop across the measured coil (shows a voltmeter in the diagram).
It is also worth talking about a technique that allows you to determine the location of the interturn circuit. This is done in the following way:
The stator, freed from the rotor, is connected through a transformer to a reduced power supply, after placing a steel ball to it (for example, from a bearing). If the coils are working, the ball will cyclically move along the inner surface without stopping. In the presence of an interturn short circuit, it will “stick” to this place.
Features of the repair of collector drives
This type of electric machine is more likely to experience mechanical failures. For example, erasing brushes or clogging of collector contacts. In such situations, the repair comes down to cleaning the contact mechanism or replacing the graphite brushes.
Testing the electrical part is reduced to checking the resistance of the armature winding. In this case, the probes of the device are two adjacent contacts (lamellas) of the collector, after taking readings, a measurement is made further in a circle.
The displayed resistance should be approximately the same (taking into account the error of the device). If a serious deviation is observed, then this indicates that there is an inter-turn short circuit or a break, therefore, rewinding is necessary.
Winding data of electric motors
This is reference data, so the most reliable way to obtain such information, refer to the relevant sources. This data can also be given in the passport to the product.
On the network you can find tips in which it is recommended to manually count the turns and measure the diameter of the wire when rewinding. It's a waste of time. It is much easier and more reliable to find the entire engine by marking the engine. necessary information, which will contain the following parameters:
- nominal operating characteristics (voltage, power, current consumption, speed, etc.);
- the number of wires for one groove;
- Ø wire (as a rule, insulation is not taken into account in this indicator);
- information about the outer and inner diameter of the stator;
- number of grooves;
- with what step the winding is performed;
- rotor dimensions, etc.
Below is a fragment of a table with winding data for electric machines of type 5A.
Do-it-yourself step-by-step instructions for rewinding an electric motor
It is necessary to immediately warn that without special equipment and work skills, rewinding coils will most likely be a futile exercise. On the other hand, a negative experience is also an experience. Understanding the complexity of a process is the best explanation for its cost.
The first stage - dismantling
We give an algorithm of actions for asynchronous machines, it is as follows:
- Disconnect the drive from the mains (380 or 220 V).
- We dismantle the electric motor from the structure where it was installed.
- Remove the rear protective cover of the cooling fan.
- We dismantle the impeller.
- We unscrew the fastening of the end caps, and then remove them. It is desirable to start from the front part, after its dismantling, the rotor will easily “come out” from the rear cover.
- We take out the rotor.
This process can be greatly facilitated by using a special device - a puller. With it, it is easy to release the motor shaft from the pulley or gear, and also remove the end caps.
We will not give instructions for disassembling the collector engine, since it does not differ much. The structure of this type of electric machine can be found on our website.
Stage two - winding removal
The sequence of actions is as follows:
- With the help of a knife, we remove the bandage fasteners and the insulating coating from the places where the wires are connected. In some instructions, it is recommended to fix the wiring diagram, for example, by taking a photograph. There is no point in doing this, because it reference Information and recognize it by the brand of the engine is not a problem.
- Using a chisel, we knock off the tops of the wires from each end of the stator.
- We release the grooves using a punch of the appropriate diameter.
- We clean the stator from dirt, soot, impregnation varnish.
At this stage, we recommend stopping, picking up the hull and taking it to the experts. Do-it-yourself dismantling will reduce the cost restoration work. As mentioned above, it is quite difficult to rewind coils without special equipment. To understand the complexity of the process, we describe its technology, which will make it easier to choose.
Stator rewind (final phase)
The process consists of the following steps:
If only the body was handed over for restoration, we recommend that you check the coils before turning on the motor.
Anchor rewind
The process of replacing the winding of the collector motor is somewhat similar, with the exception of small nuances associated with the design feature. For example, the armature is sent for rewinding, not the case, provided that the problem did not arise with the excitation coils. In addition, there are the following differences:
- For winding, a special machine of a more complex configuration is used.
- It is imperative to turn, balance the anchor (in the final part of the process), as well as its cleaning and grinding.
- With the help of a special milling machine manifold is cut.
For these processes, special equipment is required; without it, rewinding electric motors is a waste of time.
Household rotors are often used in various tools. They are direct and alternating current. Rewinding an electric motor at home in such devices is quite difficult. First, the units are disassembled with the folding of all bolts in a box. It is recommended to put a magnet on its bottom so that the bolts, studs and nuts are not lost.
Fault definition
The DC rotors of screwdrivers, mixers and fans are collector and brushless. For the latest motors, the switching of the windings located on the stator occurs using the controller. Therefore, before rewinding, it is necessary to make sure that the keys and the controller itself are in good condition. AC electric motors are divided into:
- asynchronous with a squirrel-cage rotor;
- synchronous or brush with a phase rotor.
To determine the malfunction of the rotor windings, a special induction device is used. Install broken windings induction motor You can use a tester or ohmmeter. Sometimes specialized electronic devices to detect short-circuited turns.
The failure of the rotors is most often due to a short circuit in the armature. Soldering the conductors from the contact group and checking them for a short circuit, they find a malfunction of the contacts or turns of the rotor. In the event of a short circuit of the latter, the breakdown is eliminated by replacing the wire. If there are few turns, and the rotor wire is thick and without damage, then they make it good insulation by placing a plate of cardboard or cloth moistened with insulating varnish.
In the event of a short circuit in the contact group, it must be repaired or replaced. You can cut a thin groove between the closed contacts and insert a textolite plate glued with epoxy glue. sandpaper eliminate irregularities on the contact group.
Process Features
To rewind electric motors with your own hands, you must have at least a minimal understanding of how to connect motor windings. If rewinding is done for the first time, you need to study this issue well. You should also pay special attention to the polarity of the windings and the direction of movement of the turns.
With some factory coils, the wire is first wound in one direction and then returned back. When disassembling, it is necessary to unwind 10 turns one by one, freeing the coil from insulation, and then accurately determine and record the direction of the turns in the winding.
Work with the stator
First, they draw up a diagram of the location and connection of the motor windings. If the motor is three-phase, then carefully draw up a coil circuit for each phase. They are usually wound with one wire. Only after good study and correct compilation winding connection diagrams, you can proceed to disassemble and remove them. Better mark the windings different paint and take a photo. You also need to check whether you can figure it out from photographs and diagrams.
Before rewinding the motor stator, a template is made according to its size. The width is equal to the size between the grooves in which the coil will fit. To isolate the stator from the winding, plates made of cardboard or special insulating material. When laying the coil in the grooves, use a wooden or plastic spatula - a rammer.
After winding one coil, the wire is not bitten off, the coil is placed in the grooves and continues to be wound onto the template . All coils of one phase are wound with a solid wire without biting it. First, all the turns of one of the phases are rewound, stacking them one by one. Coils for the remaining phases are wound and laid in the same way. top the windings in the stator slots above the turns are covered with plates of the same insulating material as in the stator slots themselves.
After winding and laying the coils of one of the phases, it is imperative to tie and form the coils into even bundles, trying to ensure that the turns are in the same bundle and do not touch the stator housing. If the coil is too big and touches the body, then a cut cambric is put on it, after which it is tied. Touching the wires of the housing outside the insulation is unacceptable, since during vibration from electromagnetic field the varnish may rub off, causing the coil to short to the housing. After installation, check the resistance with an ohmmeter.
The number of turns in all coils must be precisely observed in order to avoid overheating of some windings. Special attention and accuracy are necessary to avoid overlapping turns in the winding. In addition, it is necessary to ensure that the wire is not tied into a coiled knot and is not with wiped insulation. All elements that extend beyond the body of the grooves are carefully tamped.
The conclusions from the coils are filled into insulating tubes - cambric. They must not only be of a material with good insulation, but must be resistant to heating of the wire. In order to avoid melting, an insulation class no lower than previously used is required. Insulation temperature classes:
Checking and assembly
Next, they assemble the engine, having made the main bolts for “ringing” and checking the currents of each phase. With the help of current clamps, the currents of the windings of each of the phases are checked through the load and circuit breaker. They must be the same. Then the engine is assembled by tightening all the bolts and checking it for proper rotation and idling.
If everything works fine, then the mechanism is disassembled again to coat the stator windings with varnish. The stator is placed in varnish to impregnate the windings and fill voids. Then it is lifted, allowing the varnish to drain, and dried on outdoors or in a special dryer. To speed up drying, an incandescent lamp with a power of 0.5-1 kW is used, inserted into the stator and connected to the network.
After drying the engine, it is fully assembled, the insulation resistance is checked again. Do an idle check of the engine. It is better to use a step-down transformer and a circuit breaker (preferably an RCD) for this purpose. Only after checking can the motor be used at full voltage.
The following tips from experts will help you to rewind correctly:
When carrying out all work, it is necessary to use serviceable tools, as well as known to be in good working order. measuring instruments and testers. Particular attention should be paid to the serviceability of the protection of the batteries., the quality of the insulation and the humidity of the materials used during the repair.
Compliance with safety regulations and the rules for using the tool is an indispensable condition for testing. It is better to invite a specialist with extensive experience with electric motors for this.
Electric motors are used in everyday life and small workshops. Sometimes they go out of order. This article will help you determine if you can repair them yourself, or if you need to contact the master. Malfunctions of electric motors can be divided into two groups - mechanical, for example, a jammed bearing or a broken shaft, and electrical - mechanical breakage of the winding or its failure due to overheating of the electric motor.
Motor failures
There are many reasons why a motor may overheat. but the main reason is this is an incorrectly selected protection against exceeding the rated current or its complete absence.
Electric motors used in everyday life can be divided into two groups
- asynchronous with squirrel-cage or with a phase rotor, automotive generators
- collector electric motors of direct and alternating current
Each type of electric motor has its own characteristics when rewinding burnt windings.
Asynchronous motors with squirrel-cage or phase rotor
Before repair, the electric motor must be cleaned with a rag from dust and dirt. The cleaned engine is subjected to complete disassembly. Before replacing the windings, the pulley or coupling located on the front shaft of the electric motor can be left on, but the condition of the front bearing cannot be assessed with them. Failed motor bearings can be cause of engine failure.
In the absence of burnt places and a characteristic smell, the windings are disconnected from each other and the insulation is called with a megohmmeter relative to each other and the housing and the integrity is checked with 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 the wire coming out of the engine breaks. In this case, it can be re-soldered or replaced.
In the absence of breaks and integral insulation possible malfunction- This interturn short circuit. In three-phase electric motors connected to a three-phase network, this is checked quite simply. It is necessary to measure the current on all phases one by one with a clamp meter or an ammeter, or, if possible, then simultaneously. The difference in values by 2–3 times clearly indicates an interturn circuit and the need for rewinding. The same methods check the rotor in electric motors with a phase rotor.
In single-phase or three-phase motors, but connected to a single-phase network, a coil circuit is indicated by strong heating when turned on without load, provided there are no breaks, insulation failures, mechanical malfunctions of the motor and starting equipment. For example, a single-phase motor on old washing machines heats up when the starting winding is constantly on.
If the decision is made to rewind the motor, it is best to contact for repair to a specialized workshop. In "home" conditions, it is very difficult to perform this work with high quality, which can lead to its rapid failure. But if there is a need or desire to repair the electric motor with your own hands, then on youtube, at the request of “rewinding electric motors with your own hands”, you can find videos with detailed instructions.
rewind
The rewinding process can be divided into three stages
- Disassembly
- winding
- Assembly
Disassembly
It is necessary to continue disassembling and remove the windings - completely or, if the design allows, only damaged ones, in order to rewind only them. Before complete removal, cut the threads tying the wires together and sketch the connection diagram. The easiest way to remove old windings is by burning gas burner or at the stake. You can put the stator "on the butt" on bricks, fill it with firewood and set it on fire.
You can also remove the windings with a chisel and hammer, but in this case it is more difficult determine the wiring diagram 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 in the same way, but before burning out, the slip rings must be removed.
The scorched windings are carefully removed from the grooves, trying to keep at least one intact. This is necessary to determine the dimensions of the winding, the cross section of the wire and the number of turns. When disassembling, also sketch laying scheme windings in grooves indicating the direction of winding. If the motor type is known, repair data can be found in the appropriate manuals.
winding
Knowing the number of windings, the size of each and the number of turns, by multiplication, you can determine the desired length of the wire. The cross section of the wire is taken the same as on the burnt 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 more, then the wire may not fit in its grooves.
The winding of the windings is carried out on a machine similar to those machines on which the transformer coils are wound. After winding the right amount turns, the winding is removed from the machine, tied with a winding thread and set aside. The process repeats as many times as needed windings.
New gaskets made of electrically insulating material are inserted into the grooves. These gaskets are called "sleeves". Thickness and material can be determined from the reference book. If there is no data on the rewound motor, you can take it 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 winding. If two windings fit into one groove, and strips of insulating material are laid at the points of contact.
For laying the wire in the grooves, a special tool is used - a rammer. The stacked windings are fixed with gaskets made of 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 sleeves, and the width is half that.
The fixed windings are interconnected by twists, which are soldered. To those conclusions to which voltage will be applied, connect wires of the appropriate section and length. They need to be labeled indicating the beginning and end.
The connected windings are tied with winding thread or twine. The wires are brought out through the hole 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 impregnation and drying temperatures depend on the varnish used and are indicated in the instructions.
The phase rotor is rewound in the same way, only slip rings are put on the motor shaft, to which wires are connected.
Assembly
The assembled and dried engine can be collected. Before assembly, check the bearings and, if necessary, change the lubricant in them or the bearings themselves. After assembly, the motor is checked for insulation integrity and operability in idle and under load, with current measurement in all phases.
Collector electric motors of direct and alternating current
First of all, the malfunction is visible by the increased sparking on the collector and heating. First you need to clean, and if necessary, pierce and track the collector. If this does not help, then you need to sequentially measure the resistance with an ohmmeter in series between all adjacent collector plates. If the values differ significantly from each other, then the collector or turn in the armature windings (in the AC motor - rotor) has failed. 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 excitation windings are checked for integrity with an ohmmeter and for a turn short circuit. To do this, they are connected in series, if necessary, shorting the brushes or stripping the insulation on the connecting wires. A reduced 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 the winding of an asynchronous motor to a hybrid winding "Slavyanka"
When rewinding a brushless motor, it can be rewound using the “Slavyanka” technology. The method consists in winding additional stator windings with thin wire. Motors wound using this method have increased starting and operating torque, overload capacity and efficiency, reduced starting current and noise level. Due to the "soft" load characteristics, they are used in electric vehicles.
Many household appliances today use electric motors. Their main feature is that they work asynchronously. This allows you to keep a constant rotor speed even with varying loads.
All manufactured electric motors have different design features. Each modification may differ in the number of poles, rotor type, and others. constituent parts. The technology of rewinding electric motors is done according to general principle, there may be differences in some nuances.
If the device is out of order, then you need to contact the workshop. In its absence, you can try to rewind the engine at home. It is desirable to have the necessary skills for this, but in general this process is not so complicated in appearance.
"Engines" have two types of winding:
- stator;
- rotary.
Considering that the design and dimensions of the devices are different, we can give general instruction for rewinding motors. Let us dwell on those that are used in household appliances and are powered by alternating current.
Engine inspection
In the event of a breakdown, remove the engine from household appliance. Having cleared constituent elements, held visual inspection windings. The main thing is to determine exactly where the breakdown occurred. Sometimes it happens that the rotor and stator windings burn out. And then they need to be completely replaced.
When a malfunction occurs, the temperature inside the motor housing rises. This leads to a violation of the insulation on all elements. Therefore, in the repair of an electric motor, windings and insulating coatings are replaced.
Preparatory work
First, let's figure out how to properly rewind an electric motor. The first thing to do is to determine the parameters of the wire and the number of turns in the coil. The Internet will help here. On the forums, people discuss similar problems, as well as talk about personal experience how they rewind the engines.
IMPORTANT! It is necessary to find exactly the same model of the device, otherwise, after the repair, the "engine" may not start!
In the absence of the necessary information on the Internet, you can find it out on your own when examining the "engine". With a strong burnout of the “packings”, we find the most complete section of the winding. It needs to be cleaned.
To rid the wires of carbon deposits, use solvents. Now the "coils" should not be spared, they are no longer suitable. If it is not possible to clean the winding with a solvent, then you can burn it.
There is various schemes rewinding of electric motors. Before removing the "coils", you should pay attention to how they are interconnected. And then you can exactly copy their assembly.
The protruding top of the "laying" must be cut off. To do this, we will prepare the appropriate tool, it all depends on the cross section of the wire. The larger it is, the more serious the tool will be needed. The cut part must be divided into separate wires. So it is more convenient to determine the cross section and the number of turns.
Having removed the winding, we check the iron on which it was wound. The steel should be smooth without dents or burrs. Defects can damage insulating layer copper wires, which will lead to another breakdown. Therefore, all irregularities should be cleaned with sandpaper.
If there is carbon deposits in the steel grooves, you should also get rid of it. This will help to avoid further difficulties when working with insulation and wires.
How to choose a wire
In order for the power of the electric motor to be the same, a wire with the same cross section as it was should be selected. This will allow you to wind the specified number of turns.
If this cannot be done, then the most approximate cross section is taken. Ohm's law should be remembered smaller diameter conductor, the higher its resistance.
IMPORTANT! The selection of wires is taken very seriously. Incorrect section will lead to overheating of the motor, the insulating varnish will melt and as a result will lead to a short circuit!
You need to wind the winding using a template that is made independently from cardboard. It must match the size of the hardware. To achieve a neat arrangement of turns, a special wire winding machine is used. That's all it takes to rewind the engine.
Hand laying may have defects. It is possible to lay the wires loosely, which will lead to an increase in the size of the winding, and the difficulties of its installation.
Installation and impregnation
Rewinding the stator of an electric motor with your own hands does not present any particular difficulties. The main thing in this business is accuracy.
IMPORTANT! The insulation inserted into the grooves must not stick out. Therefore, the excess part is cut off, otherwise, during the operation of the engine, it may touch the rotor!
To make complete insulation of all conductive parts, a special varnish is used. On the market, it is presented in a large assortment. But in fact it is divided into two types. The first dries at ordinary temperatures, and the second only after heat treatment.
Check and enable
Before starting the engine for the first time after repair, it must be properly checked. To begin with, all the inserted "coils" ring. This will help to find out if there is a break or poor contact. Between the "laying" the resistance is measured so that when turned on there is no short circuit.
You should not immediately apply 220 V to the engine, it is better to apply a reduced voltage. Let the rotor spin slowly, the main thing here is to find out if the engine is heating up. If everything went well, and there was no smoke, then the engine repair was successful.
On the Internet there are many photos of rewinding engines. This will help beginners visually familiarize themselves with the process.
Photo of the rewinding process of electric motors
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