DIY armature rewinding diagram

DIY drill repair

- breakdown of motor parts (stator, armature) - wear of the brushes or their burning - breakdown of the regulator and reverse switch - wear of the support bearings - poor clamping in the tool chuck.

Some spare parts (switch, rotor, stator, brushes, bearings, etc.) for more popular models are bought here (but it’s better to buy through an online store, because in a regular store of this network you will like the price higher).

Replacing brushes

. The most common type of breakdown is wear of the motor brushes, which can be replaced yourself at home. Sometimes, brushes can be replaced without disassembling the drill body. For some models, it is enough to unscrew the plugs from the installation windows and install new brushes. For other models, replacement requires disassembling the housing; in this case, you must carefully remove the brush holders and remove the worn brushes from them.

Brushes are sold at all normal power tool stores, and often an extra pair of brushes is included with a new electric drill.

Don't wait for the brushes to wear down to their minimum size. This risks increasing the gap between the brush and the collector plates. As a result, increased sparking occurs, the collector plates become very hot and may move away from the base of the collector, which will lead to the need to replace the armature.

You can determine the need to replace brushes by increased sparking, which can be seen in the ventilation slots of the housing. The second way to determine this is the random jerking of the drill during operation.

Power cord

. The cord is checked with an ohmmeter, one probe is connected to the contact of the power plug, the other to the core of the cord. Lack of resistance indicates a break. In this case, repairing the drill comes down to replacing the power cord.

Electric motor diagnostics

. In second place, in terms of the number of drill breakdowns, can be placed the malfunction of engine components and, most often, the armature. Failure of an armature or stator occurs for two reasons. improper operation and poor-quality coil wire. World-famous manufacturers use expensive coil wire with double insulation with heat-resistant varnish, which significantly increases the reliability of engines. Accordingly, in cheap models the quality of insulation of the winding wire leaves much to be desired. Improper operation comes down to frequent overloading of the drill or prolonged operation without breaks to cool the engine. Repairing a drill with your own hands by rewinding the armature or stator, in this case, is impossible without special tools. Only complete replacement of the element (exclusively experienced repairmen will be able to rewind the armature or stator with their own hands).

To replace the rotor or stator, it is necessary to disassemble the housing, disconnect the wires, brushes, remove the drive gear if necessary, and remove the entire motor along with the support bearings. Replace the faulty element and install the engine in place.

An armature malfunction can be determined by a characteristic smell, an increase in sparking, and the sparks have a circular motion in the direction of movement of the armature. Pronounced burnt windings can be seen upon visual inspection. But if the engine power has dropped, but there are no signs described above, then you should resort to the help of measuring instruments. ohmmeter and megohmmeter.

Features of the asynchronous motor of the angle grinder

Almost all electrical appliances used in everyday life use an asynchronous electric motor. An important advantage of this type of motor is that when the load on it changes, the speed does not change. This means that if, for example, you cut stone for a long time and without stopping with a household grinder, there will be no noticeable external signs of engine overload. The disk rotation speed will be constant, the sound will be monophonic. Only the temperature will change, but this may not be noticed if your hands are wearing gloves.

If you are not careful, an advantage can turn into a disadvantage. Asynchronous motors are very sensitive to overheating; a significant increase in operating temperature entails melting of the insulation on the rotor windings. At first, the motor will work intermittently, and then - when an interturn short circuit occurs - the motor will stop completely. If you overheat the grinder's engine several times, it is most likely that the anchor will melt. In addition, the high temperature causes the contacts connecting the wires of the primary winding to the collector to become unsoldered, which leads to an interruption in the supply of electric current.

How to determine if an angle grinder's armature is faulty

Signs of a broken armature angle grinder are: increased sparking of the brushes on the motor commutator, vibration of the motor at low speeds, rotation of the working shaft in different directions. If such symptoms are present, you should stop using the tool - this is dangerous. Suspicions can be easily verified using simple tests.

Visual inspection from outside

Troubleshooting should begin with a visual inspection of the angle grinder:

Carry out a general inspection of the instrument.
Pay attention to the integrity of the power cord and the presence of voltage in the outlet.
Using a voltage indicator, make sure that current is flowing to the motor commutator and the start button.

Read also: What is a thicknesser used for?

Inspection of the device from the inside

If everything is in order with the power supply, but the angle grinder does not work, you will have to open the case to gain access to the motor. As a rule, disassembly is not difficult. But you need to follow simple rules that will help you avoid troubles during reassembly:

Be sure to disconnect the device from the mains before disassembling.
Remove the working disk and protective cover from the spindle.
Open the case in a well-lit place, on a clean table surface.
Remember the location of all parts and assemblies before disassembling. It is recommended to sketch or photograph the internal structure of the device.
Place screws and fastening screws in a separate place so that they do not get lost.

It is best to inspect the engine under bright lighting so that all small parts are clearly visible. The armature should rotate freely around its axis; properly functioning bearings should not make any sound during operation. There should be no traces of melted wiring on the armature, the circuit windings should be intact, without breaks. You can smell the rotor. When there is an interturn short circuit, the insulating varnish burns and emits a persistent specific odor. But such a diagnosis requires some experience.

Continuity testing of circuits with a tester

If a visual inspection does not give clear results, it is recommended to continue the examination using a multimeter. Having set the mode switch to the ohmmeter position (200 Ohm range), you need to “ring” two adjacent armature lamellas with two probes. If the resistance on all turns is the same, this means that the windings are working properly. If on some pairs the tester shows a different resistance or an open circuit, there is a malfunction in this coil.

A wire break can occur between the winding and the core. You should carefully examine the junction of the coils with the collector lamellas in the lower part of the armature, and visually check the soldering of the contacts.

Checking contacts with a light bulb

If you don’t have a tester, you can get out of the situation using a simple 12-volt light bulb. The power can be any, optimally 30–40 W. The voltage from the 12 volt battery must be applied to the plug of the angle grinder by inserting a light bulb into the gap in one wire. If the armature is working properly, if you rotate the spindle by hand, the light should light without changing brightness. If the heat changes, this is a sure sign of an interturn short circuit.

If the light does not light, this may indicate the following:

The brushes may become stuck in the non-working position. The retaining spring has worked.
There has been a break in the supply circuit.
There is a short circuit or break in the stator winding.

There are other diagnostic methods, but they require more sophisticated equipment, which is not usually used at home. An experienced technician will determine the breakdown with a high degree of accuracy using a “punch” or a simple transformer with a cut toroidal core and one primary winding.

How to quickly check the commutator motor mechanism for malfunction

Checking the element - armature , which is the main part of the commutator motor, is carried out in stages. To carry out performance testing, you need to prepare a screwdriver and a multimeter. Monitoring your condition at home can save you money.

Nuance: To improve the quality of checking the armature winding for a faulty commutator motor , it would be a good idea to buy an inexpensive device. The latter allows for in-depth monitoring of the armature core .

The initial stage is a thorough visual inspection of electrical equipment. There are situations when electrical equipment still works, but with deterioration in nominal characteristics. The latter may be a consequence of an interturn short circuit ; the result is that the part “burns.” This is easy to determine - you don’t even need to disassemble the case.

Some signs, but not the main ones, are:

strong sparking during operation of the electric motor - noticed on the traction motor commutator ;
The startup of an electric tool is accompanied by a voltage drop in the power supply network - the lighting begins to flash. Can lead to a short circuit in the entire facility;
when trying to start the electric motor, sharp jerks appear;
burnt smell of winding mechanism;
the tool cannot reach its rated power.

But it is worth noting that the above-mentioned signs show not only a breakdown of the armature of the collector unit - the engine . All of the above may indicate mechanical and electrical wear of the motor assembly brushes. Worn out, collapsed brushes are the main cause of power plant failure. Replacing them with new ones and cleaning the unit from plaque will extend the service life of power equipment.

When examining the part, there should be no traces of burning, paper, or blackening on it. The mentioned nuances are consequences of a short circuit or combustion. Prolonged presence of dust and dirt provokes a deterioration in the performance of the entire installation as a whole. Therefore, the aspect of cleanliness and maintenance must be given due attention, otherwise:

premature wear of elements increases - scale and carbon deposits negatively affect the quality of work;
the resistance of the internal parts of the electrical unit to negative environmental influences decreases.

Is the brush mechanism intact? Then the fault lies in the CD mechanism. But there are situations in which a power tool does not show signs of life - it does not start, does not react in any way to an attempt to turn it on. Let's move on to the next stage.

Complete dismantling of the tool body and disassembly

If the brushes are in order, but the cause of the breakdown cannot be determined, then disassembly of the electrical equipment will be required. The problem may lie in the internal parts of the commutator motor. First you need to pick up a screwdriver - a licked thread will not bring anything good.

The equipment has fasteners of various sizes. In order not to make a mistake, you need to remember, or better yet, sketch the bolt placement diagram. For better memory, you can take photographs of each stage of the work. This will prevent problems with the assembly of the power tool.

Household electrical appliances do not always have a complex design, and therefore the disassembly process is not particularly complex, which cannot be said about industrial electrical installations. Technical diagnostics and repair of the latter require advanced qualifications of specialists and the availability of professional testing equipment.

Preliminary preparation of the collector armature

Completed dismantling is not the final operation. The element must be prepared for further inspection. Preliminary measures will ensure the highest quality diagnostics of the component. This procedure is simple and consists of completely cleaning the slats from plaque.

The fact is that during active use, particles of work products accumulate on the surfaces of parts. This is especially true for electric motors that have been used for a long time. Plaque prevents the correct passage of current and load distribution throughout the collector complex.

Preparation is optional. But it will improve the quality of the result. Cleaning involves the use of rags and an alcohol solution. Removal of carbon deposits occurs through the action of fine-grained sandpaper. Do it carefully - any remnants of an abrasive tool will aggravate the situation with the performance of the commutator motor. Therefore, after removing carbon deposits, you need to remove traces of abrasive action with sandpaper.

Note : The mechanism must be cleaned carefully without damaging the winding . The ingress of abrasive particles and broken lamellas are aspects that increase the likelihood of an interturn short circuit in a commutator motor.

Complex processing

Processing of composite shafts is carried out in strict compliance with the second class of accuracy. The final operation is additional grinding, which does not allow the presence of transverse scratches or burrs. The mentioned abrasives significantly damage the integrity of the surface layer of the shaft.

Close attention is paid to the transition fillets - they need to be polished to a shine. This ensures uninterrupted operation of both the individual device and the entire installation as a whole. The coefficient of compression of the surface of the shaft and bushing is also reduced - necessary for an accurate fit of the anchor bushing to the shaft. In connection with the latter, diameter ledges are made along the seats.

Visual inspection before testing

Here you need to carefully inspect the manifold and the CD part. If the latter has significant depletion, then repair will not help, only replacement is relevant. The presence of a large accumulation of carbon deposits on the windings of the device and its contacts is a sign of a deep malfunction of the part. There are several ways to solve this. The first is complete rewinding, according to the winding diagram of the armature of the commutator mechanism - the engine . It will take a long and painful time to do, and the second is installing a new part. The choice is, of course, yours.

Fast and high-quality inspection - emphasis on specific details, allowing you to comprehensively determine the breakdown of elements. Pay attention to elements such as:

collector lamellas are parts on which carbon deposits often accumulate. Constant contact wears them out, and therefore if there is significant wear, there is a high probability of further motor failure;
armature windings – breaks, traces of interturn short circuit and conductor burning;
contact elements of the power unit - windings are connected to the lamellas by soldering. These places must be carefully checked for integrity. Breakdowns of contacts are fraught with deterioration in the performance of the electric motor.

After completing the visual inspection of the part, you can begin using the diagnostic equipment.

Monitoring performance with a radio multimeter

The use of a measuring device is a mandatory aspect. Without it, alas, it will be almost impossible to correctly determine the problem and the cause of the malfunction. Directly using a multimeter is divided into several stages, usually there are two. The first involves checking for the presence of a breakdown. How it's done:

The device is set to check the electrical circuit, accompanied by a sound indication;
one probe of the device acts on each part, and the second – on the body of the power element.

The second stage involves measuring the resistance that arises between adjacent windings. This is done very easily - the multimeter is set to resistance detection mode at the minimum range - usually set to 200 Ohms. Probes are the contact parts of a radio-technical device and are placed on the lamellas of the commutator.

The device reads the resistance parameters and transfers them to the screen. Next, the measured characteristics are recorded (it is better to write them down so as not to forget). The resistance should be the same between all lamellas. If this is not the case, then the commutator motor mechanism is faulty. Lack of resistance is a factor confirming a performance problem.

Diagnostics for determining interturn short circuit (MF)

One of the main causes of breakdowns is a short circuit between the turns. It is formed due to increased load on the motor, exceeding the maximum permissible parameter. The windings of the stationary mechanism - the stator - heat up, the increased temperature conditions trigger degenerative insulation processes, and as a result, MF occurs. Incorrect operating specifications lead to a significant increase in the load on the equipment.

Tip : Before using the motor, read the passport information. It indicates acceptable parameters under which the application will not have a destructive effect.

Excessive load is formed due to breakdown of the mechanical part. Bearings often jam, which leads to short-circuiting of the armature coil turns. This problem may arise due to manufacturing defects or be a consequence of poor-quality repair work.

Determine MH:

check the stator temperature - uneven heating confirms a breakdown;
measure the load of each phase. The difference may be a sign of a broken element.

As in the case of continuity testing, the MH is checked with a multimeter or megger. There is a more accurate method - using a transformer using step-down technology:

Three phases of the transformer are connected to the stator;
Next, the ball is thrown into the stator. If the ball runs in a circle, then everything is fine, if not, it is magnetized - a short circuit.

Instead of a ball, a plate is used. In the place where the MS occurs, vibration occurs. If the armature is working properly, the element is simply magnetized to the iron. Don't forget about grounding.

The MF is easily determined using a specialized device, which is a transformer with a cut-out core. Placement in the slot causes the component to function as a secondary winding. During an interturn short circuit, the plate located at the top vibrates or is magnetic to the body. After eliminating the problem, it is necessary to re-check using the above method.

In what cases can you save an anchor and restore it yourself?

If damage to the armature is determined with guaranteed accuracy, the part must be removed from the electric motor. Disassembling the motor must be done with special care, after removing the brushes and disconnecting the power terminals. The rotor is removed along with the support bearings and the motor cooling impeller; they form a single whole with it.

If most of the wiring in the armature is damaged and the balancing is disrupted as a result of overheating, it is better to replace it entirely. An imbalance is indicated by increased vibration and an uneven hum when the mechanism operates.

How to rewind an anchor - step-by-step instructions

If the balancing of the armature is not disturbed, and the problem is only in damaged windings, then such an armature can be restored independently by rewinding the coils. Rewinding a rotor at home requires a lot of patience and accuracy.

The technician must have skills in working with a soldering iron and instruments for diagnosing electrical circuits. If you are unsure of your abilities, it is better to take the engine to a workshop for repairs or replace the entire armature yourself.

To rewind the anchor yourself you will need:

wire for a new winding. A copper core with a diameter exactly matching the old conductor is used;
dielectric paper for insulating the winding from the core;
varnish for filling coils;
soldering iron with tin-lead solder and rosin.

Before rewinding, it is important to count the number of turns of wire in the winding and wind the same amount of new conductor onto the coils.

The rewinding process consists of the following steps:

Dismantling old windings. They must be carefully removed without damaging the metal body of the armature. If any burrs or damage are found on the body, they must be smoothed out with a file or sanded with emery. Sometimes, to completely clean the body of slag, craftsmen prefer to burn it with a torch.
Preparing the collector for connecting a new wire. There is no need to remove the manifold. You should inspect the lamellas and measure the resistance of the contacts in relation to the housing with a megger or multimeter. It should be no more than 0.25 MOhm.
Removing old wiring on the manifold. Carefully remove the remaining wires and cut grooves in the contacts. In the future, the ends of the coil wires will be inserted into the grooves.
Installation of sleeves for anchors. The sleeves are made of dielectric material 0.3 mm thick, for example, electrical cardboard. Cut a certain number of sleeves and insert them into the grooves of the cleaned anchor.
Rewinding reels. The end of the new conductor is soldered to the end of the lamella and wound in successive circular movements, counterclockwise. This laying is called “laying to the right.” Winding Repeat for all coils. Near the collector, tie the wires together with a thick thread of cotton fabric (it is prohibited to use nylon, as it melts when heated).
Checking the winding quality. After laying all the windings, check with a multimeter for the absence of interturn short circuits and possible breaks.
Finishing processing. Treat the finished coil with varnish or epoxy resin to secure the winding. In factory conditions, the impregnation is dried in special ovens. You can do this at home in the oven. As an option, use quick-drying varnishes for impregnation, applying the coating in several layers.

Read also: Channel weight per linear meter table

The procedure for disassembling, repairing, and assembling a hammer drill rotor

Here is the sequence for repairing a rotor with a short circuit in the windings:

Trimming the front part of the windings.
Removing the collector and frontal parts and measuring the diameter of the wire being removed.
Removal and cleaning of groove insulation, counting the number of turns along the sections.
Selection of a new collector.
Installation of a new collector.
Production of blanks from insulating material.
Installing sleeves into grooves.
Winding the anchor.
Wiring of conclusions.
Heat shrink process.
Shell reservation.
Shell impregnation.
Collector impregnation
Milling the slots of the commutator lamellas
Balancing
Cleaning and grinding the rotor.

Now let's look at everything in order.

Stage I

At the first stage, the collector must be removed from the armature. The commutator is removed after boring or sawing the end parts of the winding.

Cutting the frontal parts of the winding

If you are repairing a rotary hammer yourself, you can cut the frontal parts of the winding using a hacksaw. Clamping the rotor in a vice through the aluminum spacers, saw the frontal parts of the winding in a circle, as shown in the photo.

Replacing the anchor yourself at home

Practice shows that if you decide to replace the armature of an angle grinder, then it is best to change it together with the support bearings and the engine cooling impeller.

To replace you will need:

New angle grinder anchor. Must match your model. Interchange with other models is not permitted.
Screwdrivers, wrenches.
A soft brush and cloth for wiping the mechanism.

How to remove an anchor

Replacing the anchor begins with disassembling the angle grinder. The following steps are performed:

Use a screwdriver to unscrew the brush units on both sides. The brushes are removed.

Video: replacing bearings on an angle grinder

How to put an anchor in place

To install a new angle grinder anchor in place, you should take a new part, and then assemble the tool in the reverse order. The sequence of actions is as follows:

A fixation disk is installed on the armature shaft.
The bearing is installed using the pressing method.
The small gear is fitted and secured with a retaining ring.
The anchor is inserted into the gearbox housing, and the docking holes are aligned.
The gearbox mounting bolts are tightened.
The anchor with the gearbox is inserted into the body of the angle grinder and fixed.
The brushes are deposited in their places and closed with lids.

After completing these steps, the grinder is ready for work. The anchor has been replaced.

Video: how to check an angle grinder

An ancient Sufi wisdom says: “A smart person is one who is able to come out of a difficult situation with dignity. But the one who does not find himself in such a situation is wise.” By following the rules for operating household appliances and preventing the motor from overheating, you can avoid breakdowns and troubles in the operation of the angle grinder. Keeping and storing the tool clean and dry will prevent its mechanisms from contamination and oxidation of current-carrying elements. Timely maintenance of the tool is guaranteed to eliminate unpleasant surprises during operation.

In many household devices and home-made structures, low-power electric machines are used as a drive. 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.

Features of repairing an asynchronous machine

Engine problems of any type 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 cover). If the malfunction is not corrected in time, the shaft may jam, which will inevitably lead to failure of the stator windings. In this case, the thermal protection of the circuit breaker may not have time to operate.

“Burnt” wires of the stator winding

Based on practice, in 90% of failures of asynchronous machines, problems arise with the stator winding (break, interturn short circuit, short circuit to the frame). In this case, the short-circuited armature, as a rule, remains in working condition. Therefore, even if the damage is mechanical, it is necessary to check the electrical part.

Laying diagram, winding Interskol 230, Makita 9558HN or 9558BN and other models

The order of winding the rotor windings depends on the number of slots in the rotor core and the commutator lamellas. The parameters that determine the location of the winding wire on the rotor include winding direction and pitch . The rotation of the spindle shaft (right or left) is precisely related to the choice of which direction the wire is laid. When performing rotor repairs, it is necessary to record the above data of the burnt winding.

Important : visually identify the topmost coil and start unwinding the end from it in order to determine the layout of the winding wire. Maintaining the old pattern is a determining factor in successful anchor repair.

The number of turns and the diameter of the wire are fixed after removing the front part of the failed winding, which will allow you to carefully remove the complete bundle of wire located in the groove.

Most of the used grinders, regardless of the model (Interskol, Makita and others), are structurally made with 24 slats and a core with 12 grooves. The winding pitch is chosen to be 6.

12 grooves and 24 slats

Rotor for INTERSKOL USHM-2300M, HAMMER. Photo 220Volt

The rotor winding with such design parameters is performed as follows.

The direction of the winding is set (usually clockwise when viewed from the commutator side).
Insulation made of electrical cardboard and other similar material is installed in the cleaned grooves . The winding wire is soldered to lamella No. 1 in accordance with the old installation scheme.
The wire is placed in groove No. 1 opposite the lamella indicated by the first number and, according to the winding pitch, is directed into groove No. 6 and returning back. The number of such layings corresponds to the size of the winding turns.
A circuit with 12 grooves and 24 lamellas is built after soldering the middle of the winding to lamella No. 2 and continuing to wind the winding wire into the same groove. The required number of turns is maintained and soldering is carried out to lamella No. 3. This is how the first complete reel is obtained.
Next, winding is carried out in slots No. 2 and No. 7 , soldering the middle of the winding to lamella No. 4 and the end of the winding to lamella No. 5.
By winding the coils using the above method, the last of which ends on lamella No. 1, all 12 grooves and 24 lamellas will be involved in the laying pattern.

Winding check

In most cases, the problem can be detected by its appearance and characteristic odor (see Figure 1). If the fault cannot be determined empirically, we proceed to diagnostics, which begins with a continuity test. If one is found, the engine is disassembled (this process will be described separately) and the connections are thoroughly inspected. When no defect is detected, a break can be established in one of the coils, which requires rewinding.

If the continuity test does not show a break, you should proceed to measuring the winding resistance, 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 taken into account that the resistance of the stator coils is quite low, so to measure it it makes no sense to use devices with a low accuracy class, such as most multimeters. You can correct the situation by assembling a simple circuit using a potentiometer with the addition of an additional power source, for example a car battery.

Circuit for measuring winding resistance

The measurement procedure is as follows:

The drive coil is connected to the circuit presented above.
The potentiometer sets the current to 1 A.
The coil resistance is calculated using the following formula: , where RK and UPIT were described in Figure 2. R is the resistance of the potentiometer, and is the voltage drop across the measured coil (shown by a voltmeter in the diagram).

It is also worth talking about a technique that allows you to determine the location of the interturn short circuit. This is done as follows:

The stator, freed from the rotor, is connected through a transformer to a reduced power supply, having previously placed a steel ball on it (for example, from a bearing). If the coils are working, the ball will move cyclically along the inner surface without stopping. If there is an interturn short circuit, it will “stick” to this place.

Where to begin?

Since the structure of the rotary hammer is simple, the repair of the makita rotary hammer must begin with its disassembly. It is best to disassemble the hammer drill according to the already proven procedure.

Algorithm for disassembling a hammer drill:

Remove the back cover on the handle.
Remove the electric carbon brushes.
Disconnect the mechanical block housing and the stator housing.
Disconnect the rotor from the mechanical unit.
Remove the stator from the stator housing.

Remember, the stator housing is green, the mechanical unit housing with the rotor is black.

Having disconnected the rotor from the mechanical unit, we proceed to determine the nature of the malfunction. Rotor Makita HR2450 pos.54; article 515668-4.

How to find a short circuit in the rotor

Since you are repairing rotary hammers yourself, you need an electrical diagram for a Makita 2450, 2470 rotary hammer.

Makita 2470, 2450 rotary hammers use AC commutator motors.

Determining the integrity of a brushed motor begins with a general visual inspection. The faulty rotor pos. 54 shows traces of burnt windings, scratches on the commutator, and traces of burning on the commutator lamellas. A short circuit can only be detected in a rotor whose circuit does not have an open circuit.

To determine a short circuit (SC), it is best to use a special device IK-32.

Checking the armature for short circuit using a homemade indicator

After making sure, using the specified device or a homemade device, that the rotor has a short circuit between the turns, proceed to disassemble it.

Rotors before disassembly

Before disassembling, be sure to fix the winding direction. This is done very simply. Looking at the end of the rotor from the commutator side, you will see the winding direction. There are two winding directions: clockwise and counterclockwise. Record and write down, you will definitely need this data when winding yourself. The rotor of the Makita rotary hammer has a clockwise winding direction, right.

Features of repair of commutator drives

This type of electric machine is more likely to experience mechanical failures. For example, brushes worn out or commutator contacts clogged. In such situations, repairs come down to cleaning the contact mechanism or replacing graphite brushes.

Read also: How to drill out a soured bolt

Testing the electrical part comes down to checking the resistance of the armature winding. In this case, the probes of the device are applied to two adjacent contacts (lamellas) of the collector, after taking readings, measurements are taken further in a circle.

Checking the armature winding of a commutator motor

The displayed resistance should be approximately the same (taking into account the instrument error). If a serious deviation is observed, then this indicates that there is an interturn short circuit or open circuit, therefore, rewinding is necessary.

How to check with a multimeter

Set the resistance to 200 ohms. Connect the probes of the device with two adjacent lamellas. If the resistance is the same between all adjacent plates, then the winding is working. If the resistance is less than 1 ohm and very close to zero, there is a short circuit between the turns. If the resistance is two or more times higher than average, then there is a break in the winding turns. Sometimes when there is a break, the resistance is so great that the device goes off scale. On an analog multimeter, the arrow will go all the way to the right. But digital won’t show anything.

Diagnosis of the armature winding with a multimeter

Video: how the check is carried out

If you don't have a tester, use a 12-volt light bulb with up to 40 watts.

How to check the rotor of an angle grinder using a light bulb

Take two wires and connect them to the lamp.
Make a break on the negative wire.
Apply voltage to the wires. Place the ends of the break against the collector plates and rotate it. If the light bulb lights up without changing brightness, then there is no short circuit.
Perform a short circuit test to the iron. Connect one wire to the lamellas and the other to the rotor iron. Then with the shaft. If the light is on, it means there is a ground fault. The winding closes to the rotor housing or shaft.

This procedure is similar to diagnostics with a multimeter.

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:

rated operating characteristics (voltage, power, current consumption, speed, etc.);
number of wires for one slot;
Ø wire (as a rule, insulation is not taken into account in this indicator);
information on 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.

Example of a table with winding data

Step-by-step instructions for rewinding an electric motor with your own hands

It is necessary to immediately warn that without special equipment and operating skills, rewinding reels will most likely be a useless task. On the other hand, negative experience is also experience. Understanding the complexity of a process is the best explanation of its cost.

The first stage is dismantling

We present an algorithm of actions for asynchronous machines, it is as follows:

Disconnect the drive from the network (380 or 220 V).
We remove the electric motor from the structure where it was installed.
Remove the rear cooling fan shroud.
We dismantle the impeller.
We unscrew the fastening of the end covers, and then remove them. It is advisable to start from the front part; after dismantling it, the rotor will easily “come out” from the rear cover.
We take out the rotor.

This process can be greatly simplified if you use a special device - a puller. With its help, it is easy to free the motor shaft from a pulley or gear, and also remove the end covers.

Puller for dismantling

We will not provide instructions for disassembling a commutator motor, since it is not particularly different. The structure of an electric machine of this type can be found on our website.

Stage two - removing the winding

The sequence of actions is as follows:

Using a knife, remove the bandage fasteners and insulating coating from the wire connections. Some instructions recommend recording the wiring diagram, for example, by taking a photograph. There is no particular point in doing this, since this is reference information and finding it out by engine brand is not a problem.
Using a chisel, 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, and impregnation varnish.

Stator freed from winding

At this stage, we recommend stopping, picking up the case and taking it to specialists. Independent dismantling will reduce the cost of restoration work. As mentioned above, without special equipment it is quite difficult to rewind reels efficiently. To understand the complexity of the process, we will describe its technology, which will make the choice easier.

Stator rewinding (final phase)

The process consists of the following steps:

Installation of insulators in each groove (sleeving).
The thickness of the material and its characteristics are selected from the reference book.
Winding data is determined by motor brand.
A special machine is used to wind the required number of turns of loose coils. You can find photos and parameters of homemade manual machines on the Internet, but the quality of their work is quite questionable.

Bulk Winding Machine
The coil groups are placed in the grooves, after which they are tied and connected. These processes are quite complex and are performed manually.
Impregnation is carried out. To do this, the body is heated to a temperature of 45°C - 55°C and completely immersed in a container with impregnating varnish. It makes no sense to varnish the wires, since in this case there will still be voids.
After impregnation, the body is placed in a special chamber, where drying is carried out at a temperature of 130-135°C.
Final testing of the coils with an ohmmeter.
Assembly and test run (if only the body, but also other parts and fasteners were transferred for repair).

If only the body was submitted for restoration, we recommend checking the coils before turning on the motor.

Rewinding the armature

The process of replacing the winding of a commutator motor is somewhat similar, with the exception of small nuances associated with the design features. For example, the armature is sent for rewinding, not the housing, provided that the problem does not arise with the excitation coils. In addition, there are the following differences:

For winding, a special machine with a more complex configuration is used.
Grooving, balancing of the armature (in the final part of the process), as well as its cleaning and grinding are required.
The manifold is cut using a special milling machine.

The above processes require special equipment; without it, rewinding electric motors is a waste of time.