Motors, in general, are simple mechanical devices, but rewinding induction coils is a rather complex task, feasible only for professional winders. But anyone can rewind a small, commutator motor on their own. Such motors are usually used in coffee grinders and drills.
However, inaccuracy or poorly performed rewinding of the electric motor with your own hands can render any unit unusable. And then there will be two options to correct the situation - purchase a new unit or take it to a special service for repair.
Causes and signs of stator failure
Hand-held grinders, popularly called “grinders,” can fail for various reasons.
The most common problem is the breaking of stator turns, which occurs due to too much load on the device. Now you can correct such a malfunction yourself - rewind the stator correctly. There are often cases when the cause of a breakdown is the failure of the electrical part of the device. Various factors lead to this:
- water entering the surface through which the current passes;
- power surges;
- abruptly pulling the plug out of the socket;
- high overloads and, as a result, overheating.
There is an opinion that it is impossible to rewind the stator yourself. In fact, it is enough to understand the design of the device. If you have experience in such work and the necessary knowledge, you can repair a three-phase starting device at home. Given the preparatory work, the process may take several hours.
Wire winding diagram.
Often the engine fails due to a break in the magnetic circuit, damage to the winding or armature commutator. As the voltage increases, there is an abrupt increase in spark strength. This is usually observed on only one brush. This phenomenon leads to the destruction of the wire insulation on the stator coil. If, when turned on, the disk accelerates very quickly and gains speed, this indicates a turn short circuit in the stator.
Sparks that occur during operation of the collector signal the occurrence of disturbances in the balancing of the armature. Checking the operation of the collector can be done in this way: when turned on, the sound should increase gradually with increasing voltage. There should be no vibrations. If resonance is observed, the electric motor of the angle grinder requires repair.
Windings
Before we begin to characterize the windings directly on the stator of an electric motor, let's look at what these windings are. They are a set of wire turns, which together form an electrical circuit, which in turn sums up all the electromotive powers induced in these same turns. The coil is the simplest example of such windings, where the turns are sequentially placed next to each other.
Windings are classified into the following groups according to different criteria:
- by method of application - stator and rotor. One of the key classifications;
- according to the method of arrangement in the grooves - two- and single-layer;
- according to the shape of the coils - equal-coil and concentric type;
- by type of frontal parts - two and three stripes, as well as basket (or concentric);
- by type of wire cross-section - hard (consisting of cables with rectangular conductors) and soft (made of round wires).
Many more classifications have been implemented that allow you to select a stator coil according to a certain indicator.
There are also patterned and concentric windings, all of which are single-layer. In the latter case, the winding includes coils, which are located one inside the other.
Example of a concentric winding
The exact number of coil groups is 6p. When the number of pole pairs is even, then the number of coil groups is also indicated as even. At the same time, the first half of such sets are produced with long frontal sections, and the second - with short ones. In situations in which the number is unpaired, one group is realized asymmetrical.
In a concentric winding made of the “waddling” type, groups of coils are classified into two subgroups. Such winding occurs when the q index exceeds 2 and makes it possible to reduce the levels of overhang of the frontal elements due to their more convenient placement.
Sets of coils of asymmetrical design are not used in these types of designs even if there is an even number of pairs of poles. Indicators of electrical resistance when winding cones occur through the same length of the winding components of the coils in phases:
- one phase includes all small subclasses;
- the second – middle level;
- the third is large.
This promotes some changes in the winding. For example, the front winding components of the concentric type are placed in two or three areas at once. Based on this, the windings are of the following types:
- two- or three-plane;
- two- or three-tier.
The above variations occur when the frontal parts are installed on tiers or in planes.
The frontal elements of windings using the “waddling” method are placed in 3 positions at once. These windings are often described as bobbin windings, because they are not always the same due to differences in the length of each individual front part.
Example of waddle winding
Pattern windings are implemented as symmetrical, because the coils have the same dimensions. The simplest among them are template ones, which are shown in the figure below.
Template winding
Next come the standard waddle and chain ones. We looked at their technological features a little higher.
Types of electric motors and repair features
These devices are produced in different designs. Winding failure in industry is repaired by sending the engine to a repair shop, where the engines are disassembled, cleaned, and inspected.
Then they try to rewind the faulty windings using special winding installations
. After this, the engines are assembled and tested at operating speeds, measuring no-load current and under the expected load.
Electric motors are divided into two types:
- motors with a squirrel-cage rotor are easy to manufacture, inexpensive and have a high efficiency factor;
- with a wound rotor, this design solution is used when the supply voltage is insufficient, if this power is not enough to start the device.
Malfunctions of such devices in everyday life are eliminated together with the service department or by taking the motor to a workshop. But what to do if there is no service nearby and there is no opportunity to send it to professionals for repairs?
The only option is to try to disassemble it at home and rewind it yourself. with minimal knowledge can rewind the windings
about the method of rewinding.
Disassembling the electric motor
Before disassembling, it is necessary to wet clean the motor, then clean it with a rag. Unscrew the fan cover
, remove all the bolts sequentially. After this, we compress the fan, having first unscrewed its fixing bolt.
Unscrew the stand fasteners
and fastening of flanges. Disconnect the motor connector with the terminal block. All fasteners and bolts must be folded separately so that there are no problems with assembly later. We unscrew the front flange together with the rotor and pull it out.
The different design of electric motors makes you think in advance: “Which winding has failed, the rotor or the stator.” Using ohmmeter and megohmmeter
We check the windings.
We test the motor with an ohmmeter between the three phase terminals to ensure the same resistance. We check each phase to ground with an ohmmeter; the resistance should be on the order of several megohms or higher. Then we take a megohmmeter and check the insulation resistance
each winding to the housing.
We have identified the faulty winding; in our case, the stator winding is faulty
, and the rotor has a non-separable design. Dismantling the stator is not quite a simple task, as it might seem at first glance.
If the winding has melted very badly and the electric motor has failed due to overheating, then there is no need to knock it out; it can be removed quite easily
from their mounting points. It so happens that the winding is slightly burnt or is broken, then the varnish will hold very well, and even attempts to knock it off with a chisel will not lead to complete removal of the old parts.
Alternatively, you can light a fire and heat the stator housing
so that all the varnish inside burns out. After such actions, the old deposits will fall out on their own.
It is necessary to allow the case to cool in air without resorting to liquid cooling, otherwise the case will not withstand the temperature difference
and it will crack. Cleaning of the inner surface is required until it is shiny. There should be no scale left from the melted varnish and copper.
You will need to count the number of turns and wire parameters. the winding wire for rewinding
. This wiring has special properties. They come in round and rectangular shapes.
Wiring has very low insulation resistance
. In repair shops there are mechanical devices for winding windings, wires are taken with increased insulation strength, the letter M is added to the marking. We do the rewinding ourselves, so we will take a wire with ordinary insulation with parameters corresponding to the previous one.
Checking the electric motor after repair
Next we carry out the verification procedure. First, you need to “ring” the device again, as described at the beginning of the article when diagnosing the problem. It is necessary to exclude the possibility of breakage, lack of contact and short circuit of any kind. If the engine passes these checks, it's time to start testing for functionality. To do this, do not immediately connect it to the existing power supply. In industrial facilities, the voltage is 380 V. This is quite a lot. Using a step-down transformer, you should test the operation of the motor.
If it rotates without problems and does not smoke, then the job was done correctly. The engine can be used for its intended purpose.
Thus, the instructions for rewinding an electric motor at home are complete. Good luck to everyone in your new achievements!
Motor winding data
This is a reference data, so the most reliable way to obtain this information is to consult the appropriate sources. This data can also be provided in the product passport.
You can find advice online that recommends manually counting the turns and measuring the diameter of the wire when rewinding. It's a waste of time. It is much easier and more reliable to find all the necessary information using the engine markings, which will indicate the following parameters:
Below is a fragment of a table with winding data for electric machines of type 5A.
Example of a table with winding data
Check and enable
Before starting the engine for the first time after repair, it must be thoroughly checked. To begin with, all inserted “coils” ring. This will help you find out if there is a break or poor contact. The resistance is measured between the “layings” so that a short circuit does not occur when turned on.
You should not immediately supply 220 V to the engine; it is better to supply a reduced voltage. Let the rotor spin slowly, the main thing here is to find out if the engine is overheating. If everything went well and no smoke appeared, then the engine repair was successful.
There are many photos on the Internet on rewinding motors. This will help beginners visually familiarize themselves with the process.
Working with the stator
First, they draw up a diagram of the location and connection of the electric motor windings. If the motor is three-phase, then carefully draw up a diagram of the coils for each phase. They are usually wound with one wire. Only after a good study and correct drawing up of the winding connection diagram can you begin to disassemble and remove them. It is better to mark the windings with different paints and take photographs. You also need to check whether you can figure it out from photographs and diagrams.
Before rewinding the electric motor stator, a template is made according to its size. The width is equal to the size between the grooves into which the coil will fit. To isolate the stator from the winding, plates made of cardboard or special insulating material are inserted into the grooves. When laying the coil in the grooves, use a wooden or plastic spatula - a tamper.
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 the same phase are wound with a single wire
without snacking on it. First, rewind all the turns of one of the phases, placing them one by one. The coils for the remaining phases are wound and laid in the same way. The upper part of the winding in the stator slots above the turns is 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, they must tie them and form the coils into even bundles, trying to ensure that the turns are in one 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 and then tied. Touching the housing wires outside the insulation is unacceptable, since vibration from the electromagnetic field can cause the varnish to rub off, causing the coil to short-circuit to the housing. After installation, check the resistance with an ohmmeter.
The number of turns in all coils must be strictly observed to avoid overheating of some windings
Particular attention and care are required to avoid overlapping turns in the winding. In addition, it is necessary to ensure that the wire is not tied into a twisted knot and does not have peeled insulation
All elements extending beyond the body of the grooves are carefully compacted.
The leads from the coils are inserted into insulating tubes - cambrics. They must not only be made of a material with good insulation, but also be resistant to the heat of the wire. To avoid melting, an insulation class not lower than previously used is required. Insulation temperature resistance classes:
Troubleshooting
DC rotors of screwdrivers, mixers and fans are either commutator or brushless. With the latest motors, the windings located on the stator are switched using a controller. Therefore, before rewinding, you need to make sure that the keys and the controller itself are in good working order. AC electric motors are divided into:
- asynchronous with squirrel-cage rotor;
- synchronous or brushed with a wound rotor.
To determine the malfunction of the rotor windings, a special induction device is used. You can determine if the windings of an asynchronous motor are damaged using a tester or an ohmmeter. Sometimes specialized electronic devices are used to detect short-circuited turns.
Rotor failure is most often due to a short circuit in the armature. By unsoldering the conductors from the contact group and checking them for a short circuit, they find a fault in the contacts or rotor turns. In case of 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 make it well insulated by placing a plate of cardboard or fabric moistened with insulating varnish.
If there is 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. Use sandpaper to remove irregularities on the contact group.
Disassembling the motor
Repairing an electric motor with your own hands involves disassembling the motor yourself, which is done in various ways. Sometimes it is enough to turn the engine, where exactly depends on the place where it is installed. There are times when you need to disconnect the power cable, be sure to mark the phases, otherwise when you reconnect you will have to guess which wire to connect where.
Use a puller to remove or tighten the coupling half.
Inspect the housing, pay attention to the condition of the side covers, whether there is leaking grease on them, remove them if found. If there are no traces, you can start removing the covers; there are usually 3 to 5 fasteners.
Unscrew the bolts on the covers, lightly tap the cover on one side with a small hammer, while simultaneously applying tension on the other. Perform tapping carefully so as not to break off the “ears,” which will inevitably entail additional costs. What you need to repair an engine is the accuracy and skillful actions of a technician.
Open the covers to determine if the rotor will need to be removed from the housing or if any repair work can be done on site. When the engine power is less than 17 kW, the rotor is simply pulled out and moved to the side, and if it is higher, then repairs are done on the spot.
After you have dealt with the shaft, proceed to remove the bearings and remove completely leaked grease using aviation kerosene. When the lubricant has filled the winding, it will need to be washed and dried; 1 or 2 light bulbs or a heater are used for drying.
Types of electric motor repair work are divided depending on the type of malfunction, for example: a bearing that has “turned” on the shaft, in other words, its fit has become loose; it is necessary to weld the shaft using electric welding and turn it on a lathe. If the bearing has a number lower than 309, it is soldered with tin; such repairs have fairly good results.
Let's consider an engine with a power of up to 100 kW, equipped with rolling bearings, when the engine is operating in an emergency condition, at a critical temperature, if the thermal protection does not work, the linkage bursts.
If you encounter a similar problem, follow these steps:
- Remove the remaining winding.
- Make the bandage again and apply a layer of varnish on it, then the bandage will stick to the windings, it will not dangle during operation and will last longer.
Unique electric vehicle engine – Slavyanka
Inventor Igor Korkhov from the Belgorod region created his development - the Slavyanka electric car engine - on the basis of a conventional electric motor, providing it with a unique winding.
The author's upgrade increased the power of the unit 10 times. The engine was installed on a car called Tavria E-volution-AC. He has already been registered with the traffic police. – The Slavyanka engine is our development, Russian. It weighs 29 kg and is very easy to lift. And he’s standing on the car - the wheels are slipping in 1st, 2nd, and 3rd gears. Previously, the performance of this engine was 4–5 kW, up to 30 Newtons. Now it has 45-50 kW at peak - this was achieved by “rewinding,” the inventor said.
From the original Tavria car, only the body and chassis remained. Everything else has been removed as unnecessary. A car weighing 700 kilograms “rips” from a stop in both 3rd and 4th gear, while moving almost silently.
The maximum speed of the Tavria E-volution-AC is 110 km/h, the range of movement without recharging is about one hundred kilometers. And this is just the beginning. The inventor's immediate plans include increasing all the car's performance by at least 30%. 4 years ago, the inventor quit his job and now devotes all his time to his favorite business, systematically presenting his developments abroad.
– Europeans are running around, drooling. But our developer works very hard with them - he says, first of all, we will release them in Russia. True, for some reason our Russian enterprises don’t believe in all this; they say that the parameters I sent cannot exist. But I drive this business, and cars are running around in Kyiv,” said Korkhov.
electric vehicle engine "Slavyanka"
His passion for electric motors began in childhood, the inventor says, and now in his yard he has a dozen units equipped with electric motors of his own design: from electric mopeds and an electric walk-behind tractor to solar panels. All units in the house are independently powered by solar panels. “Slavyanka” will become more powerful and lighter every year, the designer assures, and in the near future, if investors appear, his “Tavria E-volution-AC” will surpass the world-famous electric car “Tesla”.
– The most famous electric car, Tesla C, uses the same type of asynchronous motors, but not with the Slavyanka winding. Since the Slavyanka provides great advantages, we hope to outdo Tesla: in the same engine size we will get more power, more torque and greater efficiency,” says Igor Korkhov.
https://lifenews.ru/
How to repair asynchronous motors
If there are problems in the engine, then these are problems of either a mechanical or electrical nature. In the first case, a breakdown may be accompanied by strong vibration and characteristic noise. This usually indicates a bearing problem - usually in the end cap. Failure to repair the breakdown in time can result in the shaft jamming, and as a result, the stator windings will fail. At the same time, the thermal protection function of the circuit breaker may not have time to operate.
Practice shows that in approximately 90% of malfunctions of asynchronous motors, problems appear in the stator winding - in the form of a break, an interturn short circuit, or a short circuit to the frame. At this time, the short-circuited armature most often continues to function properly. Thus, if engine damage has a mechanical cause, the electrical part must be checked.
Most often, the problem can be identified by external signs and a characteristic odor (Fig. 1). If the breakdown could not be detected empirically, then we resort to diagnostics and make a continuity test for a break. If we find it, we disassemble the motor (we will talk about this in more detail later) and carefully inspect the connections. When no defects are found, we can say that we have a break in some coil. Therefore, you need to rewind.
If after testing the break is not detected, then we measure the resistance of the windings, taking into account the following nuances:
• it is necessary that the insulation resistance of the coils on the housing tends to infinity; • it is necessary that the windings of a three-phase drive show the same resistance; • it is required that for single-phase models the resistance of the starting coils exceeds these parameters of the operating windings.
You also need to remember that stator coils have very low resistance. Therefore, to measure it, there is no point in using devices that have a low accuracy class - this is the majority of multimeters. The issue can be solved if you assemble a simple circuit using a potentiometer, adding an additional power source - for example, a car battery.
How to take measurements:
• connect the drive coil to the circuit presented above; • use a potentiometer to set the current to 1 A; • calculate the coil resistance using the following formula: where R K and U PIT are described in Fig. 2. R – resistance of the potentiometer, – voltage drop across the measurement coil (shown in the diagram by a voltmeter).
How to rewind an electric motor armature at home
Before starting repairs, prepare the following tools and materials:
In order not to do unnecessary work, it is important to correctly identify the cause of equipment failure. To do this, inspect the tool and check whether current is flowing to the collector and the start button using a multimeter or indicator. If everything is in order, then you need to inspect the device from the inside.
Engine diagnostics
Disconnect the tool from the power supply and disassemble the housing. Smell the rotor. If an interturn short circuit occurs, the insulating coating melts and emits a pungent odor.
When there are no external signs of malfunction, it is worth checking the armature lamellas with a multimeter. Switch the device to ohmmeter mode and set the range to 200 ohms. Using two probes, “ring” the 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 place a lamp in the gap. Rotate the armature shaft by hand. If the light blinks, it means that an interturn short circuit has occurred. Is the lamp not on? This means that there is an open circuit or there is no resistance in one of the lamellas.
Replacing the winding and new insulation will prevent the motor from burning out. 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 record the main indicators of the engine. Count and write down: the number of armature slots and commutator lamellas. Determine the winding pitch. The most common step 1-6 is when the coil is placed in the initial groove, then in 7 and secured to 1 groove.
Some factory windings use right or left reset. For example, when winding and discarding to the right, the coil moves to the right of the initial groove. So, when the number of armature slots is 12, the winding step is 1–6 and the reset is to the right, the winding is laid in 1 slot, then in 8 and after winding the required number of turns, it is fixed in 2 slots. All this needs to be taken into account. Otherwise, the winding will be laid incorrectly, which will negatively affect the direction of rotation.
Rewinding the armature of an electric motor with your own hands will take about 4 hours. To avoid any difficulties during assembly, it is recommended to photograph the original location of the parts during each stage of work:
Rewind completed. With some skill, repairs do not take much time. If you have changed the winding for the first time, and are not entirely sure of the correct installation of the wire, then you can carry out an additional check.
Wire winding
There are several ways to rewind the stator of an asynchronous electric motor, but when choosing any of them, be sure to remember each step during disassembly. This will make the repair easier, and significantly. For winding, you will need a copper wire in varnish insulation; its cross-section should be the same as on the electric motor being repaired.
Make sure that there is no damage to the housing and magnetic circuit of the electric motor. After this, it is necessary to make sleeves and install them in the grooves on the stator. In order not to count the number of turns, or to determine the thickness, strength and heat resistance of materials for the manufacture of sleeves, you can use reference literature. To do this, you need to know the type and model of the asynchronous motor.
All work in specialized workshops is carried out on machines. The machine even calculates the number of turns. But how can you rewind an electric motor at home if there are no such conditions? You will have to calculate everything yourself, or take all the data from the service book for the electric motor.
Advantages and disadvantages of asynchronous generators
Among all the advantages of an asynchronous generator, it is worth highlighting:
- Ease of maintenance;
- Low cost;
- Low sensitivity to short circuit (short circuit);
Despite this, asynchronous generators are not very popular, the reason for this is a number of disadvantages:
- Unreliable operation under high load;
- Dependence on electrical network parameters;
- Dependence on the active-inductive nature of the load.
Motor assembly
Assembly is carried out in exactly the opposite order:
- The bearings are heated using a special transformer and then mounted; there is no need to buy a transformer - you can make it yourself.
- After installing the bearing, put the cap on the front, and then the bearing will fit into the seat provided for it.
- Heat the coupling half and put it in place, install the rotor back, using a cotter pin.
- Replace the second cap and tighten the bolts by tapping gently with a hammer or small sledgehammer.
- Rotate the shaft by hand to determine how freely it rotates; if it is skewed, the shaft will slow down.
- If everything is fine, bolt the engine and test it by performing a test run, making sure everything is aligned, and let the engine run for 15 minutes.
Knowing how to repair an asynchronous electric motor, you can repair the long-lasting electric motor of a variety of devices, such as sharpening machines or mini-sawmills. The simplest and most common problems include a blown fuse or tripped protection.
How to call
For high-quality diagnostics of the angle grinder stator, you should completely disassemble the power tool in order to remove all other structural elements, including the rotor, to ensure free access to all its parts. At the initial stage, it is necessary to perform a visual inspection. For a more complete picture, you should definitely check for defects using electrical instruments. What devices and how to ring the stator of an angle grinder are described in detail at the link “How to ring the stator of an angle grinder.”
Preparatory work
First, let's figure out how to properly rewind an electric motor. The first thing to do is determine the parameters of the wire and the number of turns in the coil. The Internet will help here. On forums, people discuss similar problems, and also talk about personal experiences of how they rewound engines.
If you don’t have the necessary information on the Internet, you can find it out yourself when inspecting the engine. In case of severe burnout of the “layings”, we find the most complete section of the winding. It needs to be cleaned.
To remove carbon deposits from wires, use solvents. Now you shouldn’t feel sorry for the “coils”, they are no longer suitable. If you cannot clean the winding with solvent, you can burn it.
There are various schemes for rewinding electric motors
Before removing the “coils”, you should pay attention to how they are connected to each other. 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. This makes it more convenient to determine the cross-section and 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 the insulating layer of copper wires, which will lead to another breakdown. Therefore, all irregularities should be smoothed out with sandpaper.
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 being done for the first time, you need to study this issue thoroughly. You should also pay special attention to the polarity of the windings and the direction of movement of the turns.
Some factory coils have the wire wound in one direction first and then returned back. When disassembling, it is necessary to unwind 10 turns individually, freeing the coil from the insulation, and then accurately determine and record the direction of the turns in the winding.
Rewinding motors of drills and grinders
To begin with, the device should be disassembled and the engine inspected. The winding should not be removed immediately: first of all, you need to find out the number of its turns. This is not difficult to do: just separate the top of the coils and cut it off. After this, you need to burn it with a burner. Now you can count the number of its turns.
If you decide to rewind the rotor yourself, then you do not need to remove the collector. It is worth examining it and measuring the value of its resistance in relation to the body (this value should not be less than 0.2 Mohm). The collector should be cleaned of what remains of the previous winding and grooves should be cut in its contact part. This is necessary in order to then insert the ends of the coils into these places and seal them.
After cleaning, the anchor must be sleeved. The sleeves are made of electrical type cardboard, 0.2 millimeters thick, after which they are inserted into the anchor grooves. Only after completing these procedures can you begin to rewind the motor coils.
If it is decided to use circular winding, then the coil should be laid in a sequential manner until all the slots are filled. The laying direction should be chosen in the direction opposite to the clock hand (if the anchor lies with the shaft towards the winder). This type of installation is called “right-hand installation”.
In the collector area, the winding is fastened with a bandage. This should be done using a thick thread of cotton fabric, laid in several tight turns and tied tightly. There is no need to use nylon threads, since nylon can easily melt during operation of the device.
After this, you need to check the product for the absence of interturn short circuits and breaks in the winding. This is best done before the product goes into impregnation, because before impregnation it is much easier to change the winding on the armature.
To secure the resulting winding, you need to impregnate it. This can be done using regular epoxy, designed to be hot cured with the addition of a plasticizer. If this procedure is performed at home, then any varnish can be used. When the impregnation is completed and dried, it is necessary to perform a grooving. How you do this will determine how much the armature will spark. The amount of beating should not be more than 5 hundredths of a millimeter, and the cutter must be properly sharpened to work with copper. After completing all these procedures, you need to re-check the product for short circuits.
Engine Inspection
In the event of a breakdown, remove the motor from the household appliance. After cleaning the components, an external inspection of the windings is carried out. The main thing is to determine exactly where the breakdown occurred. Sometimes it happens that the rotor and stator windings burn out. And then you need to completely replace them.
When a malfunction occurs, the temperature inside the motor housing increases. This leads to a breakdown of insulation on all elements. Therefore, when repairing an electric motor, the windings and insulating coatings are replaced.
We check and collect
The next stage is assembling the motor. We tighten the main bolts to make a continuity and check the current of each of the phases. Using current clamps, we check the winding currents of each phase through the load and the circuit breaker. They need to be the same. After this, we assemble the motor, tighten all the bolts and check it for correct rotation and idle operation.
If everything works, we disassemble the system again to coat the stator windings with varnish. The stator is placed in varnish to impregnate the windings and fill voids. After this, we lift it so that the varnish drips off and dry it by placing it in a special dryer or in the open air. To speed up drying, we use an incandescent lamp (power 0.5–1 kW) - we insert it into the stator and plug it into the network.
When the motor is dry, we completely reassemble it and check the insulation resistance again. We check how the electric motor works at idle. For this task, it is better to use a step-down transformer and a circuit breaker (an RCD is recommended). And only when the motor has passed the test can it be used, giving full voltage.
To carry out rewinding correctly, you should follow these recommendations from experts:
• When we determine the malfunction of an electric motor, we take into account that the insulation resistance can often decrease due to the fact that dirt or metal shavings can get on it. In this case, the motor must be carefully cleaned, rinsed from dirt and dried using a hair dryer or heat gun.
• Very often it is not necessary to do all the rewinding. In the event of a short circuit under the flanges due to vibration, the damaged insulation must be repaired. As a result, we clean and replace the insulation, after which we fill the damaged area with varnish.
• If an interturn short circuit occurs during testing, then use an ohmmeter to determine the closed turn. Once the damaged element has been identified, we replace it, solder the ends and insulate it. After this, we check the engine on the stand.
• If you want the electric motor winding to be rewound onto the template evenly, then we lay wire to wire, without making overlaps or distortions according to the dimensions of the stator. After this, we carefully check whether there are any protrusions of the winding insulation from the stator slots so that when inserting the rotor it does not catch it. There should be no turns on the wire. The brand and cross-section of the wire must be the same as the original.
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Features of the operation of a commutator motor
Universal models can be powered by both alternating and direct current. The advantage has significantly extended these units to domestic use. They are installed in various power tools, including grinders, screwdrivers, sewing and washing machines.
The windings of both components, namely the stator and the rotor, are made in series connection. Current is supplied to the last element performing rotation through special brushes. They come into contact with the commutator plates connected to the ends of the rotor coils.
The reversing effect occurs by changing the polarity of the inclusion of the stator and rotor in the power supply, and the speed is by varying the volume of current generated in the windings.
Flaws:
- a lot of noise - washing machines are proof. Modern washing machines are equipped with special parts that reduce noise;
- significant price;
- difficult control.
Machines used in everyday life are distinguished by mechanical switching with field coils (CB). The latter can be independent, parallel, or sequential. Mixed types of parts are often used. CDs equipped with permanent magnets do not have the disadvantage of high cost and management. They are easy to control, and to change the direction of rotation, just change the polarity.
Do-it-yourself rewinding of electric motors
Despite the fact that electric motors are very reliable equipment, their failure is not uncommon. Considering their considerable cost, it is much more profitable to carry out repairs than to buy a new unit.
Some craftsmen, using simple devices, do this even at home. However, it is worth noting that rewinding electric motors
requires special knowledge and skills.
We propose to consider the main operations that must be performed when performing this work.
ATTENTION! Electrical installation work should only be carried out in full compliance with safety regulations. Repair of industrial electric motors is carried out in special workshops or workshops
As a rule, each enterprise has special services that perform this work.
Repair of industrial electric motors is carried out in special workshops or workshops. As a rule, each enterprise has special services that perform this work.
Considering that the weight of industrial electric motors often reaches hundreds and even thousands of kilograms, when repairing them it is impossible to do without special equipment.
Therefore, we will not talk about them, but about compact industrial and household models, the repair of which can be done with your own hands.
Motor winding data
These are very important parameters that affect the performance of the unit. The easiest way to get them is to contact the appropriate sources, the most reliable of which is the product passport. You can also find this information by looking at the engine markings from open sources.
The electric motor data sheet must include the following:
- engine's type
- Number of phases
- Frequency Hz)
- Rated power (W or kW)
- Supply voltage (V)
- Current consumption (A)
- Speed (rpm)
- Engine efficiency
- Power factor cosφ
- Degree of protection
- Insulation class
The number of coils can be determined visually after disassembling the engine. The diameter of the enamel wire required for rewinding is measured with a caliper. And the number of turns of the enameled wire can be determined when removing the old one. To do this, the windings of the wires of one of the coils are carefully cut and recalculated.
Do-it-yourself repair and rewinding of electric motors -
sequence of actions
- Disconnection from the mains
- Dismantling from the installation site
- Removing the cooling fan guard
- Removing the fan impeller
- Disassembling the electric motor
- Removing the rotor
- Removing the winding
- Cleaning the rotor and stator from dirt, carbon deposits and impregnation residues
- Laying coils in grooves
- Winding impregnation
- Drying the electric motor
- Checking coils with an ohmmeter
- Electric motor assembly
- Trial run
Stator rewinding
As an example, rewinding an asynchronous motor. Before disassembling, the engine housing is usually wiped with a damp cloth and dried thoroughly. Winding of coil groups is done either on a special machine or manually using templates. After the coils are placed in special grooves, they must be tied and connected into a single chain.
After rewinding, the electric motor must be impregnated with a special impregnation. To do this, the body is heated to a temperature of +40-+50°C and lowered into a container with impregnating varnish. After complete drying, the resistance of the stator coils is measured (the values obtained should be the same), as well as the coils and housing are tested for breakdown.
Then the engine is assembled and a test run is performed.
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The electric motor, as one of the most heavily loaded units, very often fails.
The main cause of breakdowns is power surges and overheating, as a result of which the insulation in the winding is broken, a short circuit occurs and the copper wires simply melt. Throwing out an engine is not always the right decision, because you can get by with a major overhaul, which, of course, in most cases is cheaper than buying a new unit. Winding electric motors is a rather labor-intensive process that requires not only perseverance, but also considerable experience from the winder-repairman. What materials and tools does the specialist work with? Let's answer this question.
If you look at the winding data of electric motors, you will notice that in these tables we are talking mainly about the characteristics of the copper and aluminum wires used for winding. They are the main consumables. Each individual case requires the use of winding wires with certain technical characteristics - brand, cross-section, type of insulation, etc. (tables with winding data for electric motors contain all the necessary information on the selection of wires).
The second most important consumable is the insulation placed in the grooves of the cores between the coils (in the simplest case, between the primary and secondary), at the exit of the wires from the engine, for grouping wires, and in other cases. Insulation also has its own characteristics: operating temperature, maximum voltage and current, thickness, etc. Examples of insulating materials: glass tape, electrical cardboard, fluoroplastic film, etc. For example, according to the winding data of single-phase electric motors with E-class insulation, lavsan is used.
After successful winding of the electric motor, it is time to impregnate its wires with special impregnating liquids. They are necessary for fixing wires and insulation. Various varnishes, bitumen and polyester compounds and other substances, also different in technical parameters, are used as such materials.
The main working tool of the wrapper is the tilter. This is a mechanized machine designed for winding wires on the stators of various types of motors.
After treating the unit with impregnating materials, it must be dried so that the liquid hardens. For these purposes, drying cabinets are used (for external drying by thermoradiation), special equipment that supplies current to the winding, heating the wires and, as a result, drying the impregnating material.
Despite all the perfection of modern equipment, the process of winding electric motors is very rarely carried out without the use of hand tools, especially in the case of repair of units. Any wrapper-repairer should always have in his arsenal (see figure):
The wrapper's arsenal may also include other auxiliary tools, including traditional ones - pliers, side cutters, tweezers, etc.
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