How to calculate the number of windings in the stator of an angle grinder

What burns most often in an angle grinder.Signs of rotor burnout

As Shakespeare said, “Nothing lasts forever beneath the moon. Household appliances, alas, are no exception. It happens that even the most reliable mechanism fails. And you have to be ready to face this fact without panic, with the firm belief that there is no such thing as a hopeless situation. How is the angle grinder arranged, what can be malfunctions, how to check the motor armature, determine the cause of failure and fix the problem? Knowledge of the device of the main nodes of the power tool will allow the master with his own hands to diagnose and repair the angle grinder.

Factors that cause stator failure:

Signs by which you can understand that the stator is defective:

  • There is a smell of burning insulation.
  • The case overheats.
  • Smoke appears.
  • The rotation of the shaft slows down or stops.
  • Shaft spontaneously spins out, the tool rapidly reaches maximum speed.

The winding wires are covered with a protective layer of insulating varnish. If it overheats, it burns up and destroys. This causes a short circuit in the windings. The lacquer emits a specific smell. Short-circuiting just one of the wires completely fails the angle grinder.

Rules that will help to avoid overheating of the motor angle grinder:

  • Turn off the device after working at lower speeds not immediately, but after about one minute.
  • Take frequent breaks when working under load at reduced speed.

It is often possible to avoid replacing a faulty stator by rewinding the stator winding. Rewinding a damaged stator coil angle grinder can be done with their own hands, but it is recommended to assign this work to a specialist.

Disassembling the angle grinder

How to check the stator of an angle grinder? To begin with disassembly of the device. To perform the work you will need a screwdriver.

  • Remove all unnecessary parts from the surface on which the angle grinder will be disassembled.
  • Remove the disc.
  • Remove the screw securing the hood.
  • Remove the screws that fasten the plate.
  • Slide the hood in the direction of the cord.

The stator is on the outer side of the motor, on top of the rotor. To remove the stator, you must first remove the brushes, then remove the gearbox, and after that pull the armature out of the angle grinder housing. The rotor must be removed from the stator before testing. It is advisable to perform the inspection in bright light. The first thing to do is to carefully inspect the winding and make sure that there are no visible breaks. If the inspection does not reveal the cause of the stator malfunction, then a special tool will be needed to test.

Diagnosing malfunctions in an angle grinder

Signs of improper operation of the angle grinder for the attentive ear and sharp eye appear long before the actual failure of the tool. Before it finally breaks down, the angle grinder usually begins to give distress signals. This could be:

increased housing vibration during operation;excessive arcing of the collector brushes;heavy humming of the motor during start-up;cracking of the gearbox with broken teeth or dried up gears without lubrication;jamming of the rotor shaft bearings or their shrill creaking during acceleration;specific smell or even smoke coming from the housing of the angle grinder.

To save the angle grinder from a major and expensive repair, you should pay attention to the technical condition of the tool and respond in a timely manner to changes in its work.

If the angle grinder has the first symptoms of improper operation, it is necessary to urgently diagnose the device and find the cause of the malfunction. To do this, you need to check the two main systems of the device. electrical and mechanical.

Recommended: Circular saw. the main characteristics of the tool and features of its choice

calculate, number, windings, stator

Checking the electrical system

The electrical part of the angle grinder consists of:

the electric motor;the power button;the electronic control unit for starting and speed.

The electric motor, in turn, is divided into two main parts. the stator and the rotor (or anchor).

The task of the master is to consistently check all of these systems and discover the causes of malfunction. For this you need a multimeter or a tester.

Universal tester for electrical diagnostics angle grinder

calculate, number, windings, stator

Checking the power circuits

The first thing to do is to check the continuity of the power cord. Many mishaps can only occur because there is damage in the cable and the appliance is not powered evenly. The cord should be perfectly intact, with no signs of damage. During operation, it should not get hot or spark at the bends and connections to the socket or angle grinder. If at least one of these conditions is not met, the cord should be repaired or replaced.

Using a tester switched to voltmeter mode, check the input voltage in the angle grinder, it should correspond to the specifications: 220 В. In the ammeter mode, measure the current consumption. it should not exceed the value of 6 A.

Checking the starter and control box

The next step is to test the start button and the electronic control unit. Possibly the contact group for activating the device is oxidized or clogged. If the device is equipped with a soft start system, the drive should accelerate to operating speeds gradually, without a sudden increase in speed. Using a multimeter, make sure that the voltage is transmitted to the electric circuit when you turn on the button.

If during the operation of the angle grinder was noticed that the brushes in contact with the collector spark excessively, or the disk rotates irregularly, changing the number of revolutions per minute, then it is likely that the stator or armature windings are involved. Since the stator is less subject to overloading. it only generates the magnetic field. the motor rotor is most likely to be affected.

Diagnostics of the rotor. how to “sound” the armature with a tester?

To be sure of the serviceability of the rotor, you must “ring” it with a tester.

With the multimeter toggle switch set to 200 Ohm, measure in series the winding resistance on the two adjacent armature lamellae. If the resistance is the same everywhere, then the armature is intact and functional. If any of the pairs of lamellae shows a different value on the tester than the others, an inter-turn fault has occurred at that point. Anchor to be repaired or replaced.

Interturn faults are usually caused by overheating of the tool during operation. The windings insulation is melting, and this causes adjacent turns of copper wire to come into contact. The result is a disturbance in the balance of motive power and this leads to a loss of output at a certain armature position.

Diagnosing the stator of an electric motor

If the armature appears to be functional, then the stator should be tested with the same procedure, measuring the resistance of the windings. Short circuit in the stator is characterized by an increase in rpm of the angle grinder when it is switched on. The motor suddenly begins to rotate at an increased speed.

A defect in the insulation in the stator windings can be repaired or replaced. Repair, as a rule, consists in rewinding the copper wire.

A specially made template is used to rewind stator coils. As a rule, it is made of plywood. The size of the template is determined with a reserve of 10 mm for each frontal part. In order to prevent the wire from slipping off the plywood during winding, on the sides it is attached to the cheeks.

Rewinding can be done at home if the necessary tools and equipment are available. It is important to choose a copper conductor with a cross-section that exactly matches the original. The number of winding turns must not be changed.

Recommended: Repair of the battery of an electric screwdriver with his own hands. replacement of the batteries, checking with a multimeter

Checking the mechanical part of the machine

Gearbox; spindle locking button; flange mounting of the working tool; bearings of the rotating rotor shaft.

To determine the mechanics of the angle grinder, you must open the aluminum alloy gear housing. There are typically four screws on the gear cover that must be removed to gain access to the gear set.

Inspecting the Gears

Inspection of the gear train is to determine the strength of the gears, the presence of sufficient lubricant, and the integrity of the teeth.

Checking the detent button

Spindle lock button is a spring-loaded steel rod that prevents rotation of the work shaft. Button is used when changing cutting discs. Stem breakage usually occurs when the disc is jammed or the motor is running with the button depressed.

Lock button is used when repositioning a cutting disc or attachment

Anchor on the angle grinder: how to check the motor anchor at home

If you are certain that the armature is broken, it is necessary to take out the electric motor.

Disassemble the motor as carefully as possible. Disconnect all brushes and terminals from the power supply.

Do not forget that before you change the winding, no matter what power tool Bosch, Sparky, Makita, Interskol you need to manually establish the causes of failure of the grinder. To do this, you will be helped by the winding diagram and the reducer, as well as a special indicator. Take out the rotor, and with it the supporting bearings and cooling impeller. All this represents a single whole object. If you notice that most of the wiring is damaged and the balance is off, it is better to replace this component completely. That the balance is off can be indicated by the appearance of hum and vibration in the mechanism.

Do not take up the repair of angle grinder, if you have no basic knowledge of working with a soldering iron. In such a situation, it is better to take the instrument to a workshop and turn to a professional

If the armature balance is not disturbed, and the problem is only in the winding, then the armature is restorable. The work will consist of rewinding the coil yourself, everything must be done carefully with patience and accuracy. If the balance of the angle machine is malfunctioning, it should first be checked with a tester. In the event that the winding shows different data, it will not be possible to repair the electric motor itself. But replacing it will help.

In order to replace the rewinding in the armature you will need:

  • The new wires for the winding should be copper strands, the diameter of which will correspond to the previous wires;
  • Dielectric paper to insulate the winding;
  • Lacquer to fill the coils;
  • Soldering iron with solder and rosin.

Before rewinding, count the turns of the wire and use the same amount of wire in the new winding.

Rotor malfunctions

If it is used optimally, the rotor will not wear out. Maintenance work is performed and brushes are replaced as they wear out. But over time, with heavy loads, the stator heats up and fouling occurs. The most common mechanical failure is bearing wear or misalignment.

The angle grinder will work, but it quickly wears out the plates, and over time the motor breaks. To avoid breakage, the tool must be checked and the normal conditions of service must be maintained.

Moisture entering the metal will cause the formation of rust. The friction force increases, more current is required for work. Significant heating of contacts and solder occurs, causing a strong spark.

How to check the angle grinder armature for serviceability

If armature is defective, motor overheats, winding insulation melts, turns short-circuited. The contacts that connect the armature winding to the collector plates become unsoldered. The current stops flowing and the motor stops working.

Standard diagnostics

Before taking a tool to diagnose the problem, look at the armature. There may be some damage. If the wire is melted, there is black residue or a peculiar smell coming from the burnt insulating varnish. You may see bent or crumpled coils or conductive particles, such as solder residue. These particles are the cause of a short circuit between the coils. The lamellae have bent edges, called roosters, to connect to the winding.

A disturbance in these contacts causes the lamellas to burn out.

Other collector damage: raised, worn or burned plates. There could be graphite from the brushes accumulated between the lamellae, which also indicates a short circuit.

calculate, number, windings, stator

Angle grinder construction

Wiring diagram for a collector motor.

Anchor is a rotating part that has windings to create the desired torque that is transmitted to the motor gearbox. The stator has the same windings and is divided into several parts. Electric current comes to the winding through the carbon brush and travels to the armature. Then the current comes to the next brush and so on until all sectors of the stator are engaged.

This stator has an anchor. This element of the design of the angle grinder is considered the most difficult, because it is pressed almost all the windings.

The stator of the electric motor has the same appearance. The characteristic differences are:

As electricity flows through the armature windings it produces a magnetic field which interacts constantly with the same field of the stator. This interaction triggers an electric motor. Sometimes the stator includes permanent magnets. For example, such parts have an electric windshield wiper motor of a car. Each collector motor is capable of any kind of voltage. If you change its value, it is possible to adjust the desired number of revolutions.

Characteristic faults of the stator are considered:

When the chain works properly, the armature begins to rotate and the disc is set in motion by the gears.

Collector motor test diagram.

The gearbox maintains the required speed and speed. Repair of the angle grinder is quite affordable in domestic conditions. It is only necessary to first disassemble the device.

In order to move the hood, you need to unscrew the screw that secures the plastic plate. All parts will be in view, except the gearbox, which is concealed by a metal shroud. It prevents the gearbox from getting too hot. To remove the gearbox you need to unscrew the four screws. This exposes all the mechanical parts of the angle grinder.

When the device is plugged in and the disc accelerates at high speed, it means that the stator winding has been short-circuited. The stator requires repair, most often needs to be rewound.

Rewinding a stator seems to be a very difficult job. There is an opinion that it is almost impossible to carry out such work at home. Because sometimes even experienced motor winders refuse such work. However, with the appropriate experience and some technical knowledge, an ordinary three-phase stator can be repaired in a few hours with all the preparatory work.

Before starting repair and rewinding, the stator must be cleaned of dirt and the old winding must be removed from the grooves. This work is done with steel brushes. In addition, damaged insulation is removed. For easier cleaning of the insulation, the stator is dipped in heated transformer oil, which softens the remaining insulation.

Main malfunctions

The main faults of the stator are the following:

If you are certain that the armature is broken, it is necessary to take out the electric motor.

Disassembly of the motor should be carried out as carefully as possible. Disconnect all brushes and terminals from the power supply.

Do not forget that before you change the winding, no matter what power tool Bosch, Sparky, Makita, Interskol you need to manually establish the causes of the breakdown of the sander. A winding and gearbox diagram and a special indicator will help you do this. Remove the rotor and with it the support bearings and the cooling impeller. All this represents a single whole object. If you notice that most of the wiring is damaged and the balance is broken, it is better to replace this component completely. The appearance of hum and vibration in the mechanism can tell you that the balance is off.

Do not take up the repair of the angle grinder, if you have no basic knowledge of working with a soldering iron. In such a situation, it is better to take the device to a workshop and turn to a professional

If the armature balance is not disturbed, and the problem is only in the winding, the armature can be restored. The work will consist in rewinding the coil yourself, everything must be done carefully with patience and accuracy. If the balance of the angle machine is running erratically, it should first be checked with a tester. In the case if the counterblow shows different data, it will not be possible to repair the electric motor by yourself. But it can be restored by replacing it.

In order to replace the winding in the armature you will need:

  • The new wires for the winding should be copper wires, the diameter of which will correspond to the previous wires;
  • Dielectric type paper to insulate the winding;
  • Varnish to fill the coils;
  • Soldering iron with solder and rosin.

Before you do the rewinding, you need to count the turns of wire and apply the same amount in the new winding.

The electrical component of the construction of the angle grinder

Throughout its existence, the appearance of the tool has remained virtually unchanged. angle grinder has an oblong body, in which the electric drive and gearbox are installed. On the side surface of the tool is fixed handle to keep the tool in operating position, in addition, for the protection of the master a protective cover is attached to the body of the tool, covering the working element.

angle grinder, like any tool, can fail during operation. In most cases, to fix the failure requires a simple repair of the working equipment, its electrical component.

In order to make repairs, you need to know not only the structure of the mechanical part, but also the electrical circuit of the tool. To make a quality repair, you should study the principle of operation of the angle grinder. The electrical circuit of the angle grinder includes the following structural elements:

  • armature;
  • collector;
  • electric brushes;
  • gearbox;
  • stator;
  • start and lock button;
  • A power cable with a plug for connection to the domestic mains.

Each of the components is designed to perform a specific function in an electrical circuit, and the failure of any one of them leads to a shutdown of the device. For example, an armature is a rotating element in an electrical circuit. It transmits the rotational motion to the grinding disk. For the tool to work properly, the armature must rotate at high speed. The higher the rotational speed of this component, the higher the power of the appliance.

Winding diagram, how to choose the thickness of the wire

Grinder stators have a very similar design and differ in the size of the parts in which the magnetic flux is formed, the number of turns in the windings and the diameter of the wire. The following diagram shows a typical connection diagram for angle grinders.

Here, L1 and L2 stand for the stator coils.

Important: coils after rewinding should be installed according to the diagram above, where the beginning and ends of the windings are placed diagonally, as shown in the figure:

Burned coil is removed, in this case it is necessary to collect information about the old coils: determine the number of turns, wire diameter, beginning, end of the coil and the required direction in the rewinding work. The number of turns is determined by directly counting the wires after cutting the failed coils.

The diameter of the wire should be as close as possible to the windings to be replaced. Therefore, the most suitable measuring tool is a micrometer with an accuracy of up to 0.01 mm. Measurement should be performed on the surface of the wire of the burned-out coil, stripped of the insulation coating.

Winding diagram, how to choose the wire thickness

The stators of angle grinders are of very similar design and differ in the size of the parts where the magnetic flux is generated, the number of winding turns, and the wire diameter. A typical connection diagram for angle grinders is shown in the following illustration.

Here L1 and L2 stand for the stator coils.

Important: the coils after rewinding should be installed according to the diagram above, where the beginning and ends of the windings are placed diagonally, as shown in the figure:

The burned winding is removed, and in doing so, information about the old coils must be collected: determine the number of turns, the wire diameter, the beginning, the end of the winding and the required direction for the rewinding work. The number of turns is determined by directly counting the wires after cutting the failed coils.

calculate, number, windings, stator

the diameter of the wire should be as close as possible to the diameter of the winding to be replaced. A micrometer with an accuracy of 0.01 mm is therefore the most suitable measuring instrument. The measurement should be made on the stripped surface of the wire of the burned-out coil.

Steps of stator rewinding procedure

When working, it is important to get a strictly defined number of turns. it must be identical to the number of turns of the old winding. The wire should be wound so that the seal is as tight as possible. The coils are placed in the stator. From the same material from which the coil winding is made, the leads are made. Their ends should be insulated with kimballs. tubes made of plastic.

Before mounting the coils, it must be checked that the groove boxes are symmetrical. They should cover the winding. If this is not the case, temporary inserts are placed when laying the coil wires. This simple measure will avoid damage.

The coil is mounted over the slot that is below the bore. The conductors of the coil are installed with the help of a special plate. The wires placed in the groove should never be crossed over. They should be laid in exactly the same way, in the same sequence as the winding. Conductors must be installed strictly in parallel.

To do the next operation the stator needs to be rotated a little. only by one graduation. The coils of the same group are placed in the groove. After the laying is completed, the spacers should be put in between. Screw the leads to the outer contour so that they are parallel to the outer contour. The underside of the coils is assembled in the same way. The operation is repeated until the grooves of this step are filled.

When the winding is finished, the ends can be bent. The dimensions of the thermowells depend on the dimensions of the stator. The thickness of the sleeve is usually 0.2 mm, but the length must be greater than the size of the starting device. This is usually about 1,5 mm. A special cardboard is used to make the sleeve. Wrap the foil around the stator (it must be heat resistant). The whole resulting construction is wrapped up with scotch tape. Coils with sleeves must be installed in the slots of the stator. Then it is possible to check that the armature is moving correctly. The coil is complete. It will only have to be wrapped with a tape and coated with a layer of varnish on top. After the varnish dries, the device is fully ready for use.

When it comes to rewinding the stator, in the vast majority of cases, this means repairing the tool. As an example of carrying out the mentioned process, the stator can be rewound on an angle grinder.

The described process of replacing the windings in one of the parts of the electric motor can be carried out and domestic conditions. This can be explained by the complete rewinding of a burned-out winding. That is, choose exactly the same conductor, with exactly the same insulation.

Where to start?

Since the structure of the peorator is uncomplicated, the repair of the Makita peorator should begin with its disassembly. It is best to disassemble the stator following the tried and tested procedure.

  • Remove the back cover on the handle.
  • Remove carbon brushes.
  • Disconnect mechanical housing and stator housing.
  • Detach 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.

After disconnecting the rotor from the mechanical unit, proceed to determining the nature of the fault. Makita HR2450 rotor pos.54; part number 515668-4.

How to find a short circuit in the rotor

Because you’re doing your own repair work, you’ll need a schematic diagram of a Makita 2450, 2470.

Makita 2470, 2450 is equipped with an AC collector motor.

Determination of collector motor continuity begins with a general visual inspection. The defective rotor has a pos.54 shows signs of burned winding, scratches on the manifold, traces of burning on the manifold lamellae. Short circuit can be defined only at the rotor, in the circuit of which there is no breakage.

To find a short circuit (short circuit) it is best to use the special tool IK-32.

Checking the armature for short circuits with a homemade indicator

After making sure, using the above device or a home-made device, that the rotor has a short circuit between the coils, proceed to disassemble it.

Rotors before disassembly

Be sure to fix the winding direction before disassembly. It’s very easy to do. Looking into the face of the rotor from the manifold you can see the winding direction. There are two winding directions: clockwise and counterclockwise. Take note of this data, you will need it when you wind it yourself. The Makita rotor is wound clockwise, in the right direction.

How to Ring-Test

For a good diagnosis of the angle grinder stator, the power tool should be completely disassembled to remove all other structural elements, including the rotor, to ensure free access to all its parts. The first step is to perform a visual inspection. To get a fuller picture, you should always check for faults with an electrical tool. What tools and how to ring the stator of an angle grinder, described in detail at the link “How to ring the stator of an angle grinder”.

In most cases the problem can be detected by the external appearance and the characteristic smell of the coil (see the picture on the left). Fig. 1). If the fault cannot be found empirically, you can proceed to diagnostics, which begins with a continuity test. If it is found, the motor is disassembled (this process will be described separately) and the connections are carefully inspected. When the defect is not detected, a breakage in one of the coils can be detected, which requires rewinding.

If the dialler does not show a breakage, you should proceed to measure the resistance of the windings, with the following nuances:

  • the insulation resistance of the coils to the housing should tend to infinity;
  • In a three-phase drive, the windings should show the same resistance;
  • in single-phase machines, the resistance of the starter coils exceeds that of the working windings.

In addition, note that the resistance of the stator coils is rather low, so it makes no sense to use devices with a low accuracy class, such as most multimeters. The situation can be corrected by assembling a simple circuit on the potentiometer with the addition of an additional power source, such as a car battery.

  • The drive coil is connected to the circuit presented above.
  • Using a potentiometer, set the current to 1 A.
  • The resistance of the coil is calculated using the following formula:. where R K and U PIT were described in figure 2. R. resistance of the potentiometer. voltage drop on the coil being measured (shown by the voltmeter on the circuit).

It is also worth telling about the method that allows you to determine the location of the inter-turn short circuit. This is done as follows:

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

How to check the motor armature at home?

Anchor of the electric motor refers to the rotating part, on which dirt collects, soot forms. If any malfunctions occur, you can carry out diagnostics at home visually and with a multimeter. There must be no chips, scratches or cracks on the rubbing surfaces. If any of these are detected, measures are taken to eliminate them.

Typical malfunctions

The motor anchor is not subject to wear and tear under normal operating conditions. Replace only the brushes, measuring the allowable length. But under prolonged load, the stator windings begin to heat up, resulting in fouling.

Mechanical stresses can cause the motor armature to warp if the bearing assemblies are damaged. The motor will work, but the gradual wear of the blades or plates will lead to its final failure. But to save the expensive equipment is often enough to carry out preventive repairs and the device can be used for a long time.

Negative factors affecting the motor armature include moisture on metal surfaces. Prolonged exposure to moisture and rust is critical. Because of red buildup and dirt there is an increase in friction, this increases the current load. Contact parts get hot, the solder may flake off, creating an occasional spark.

The service center can help, but it will require a certain cost. The breakage can be dealt with independently, by reading the question: how to check the motor armature at home. A device that measures resistance and tools are needed for diagnosis.

How the fault is diagnosed?

Checking the motor armature begins with identifying the fault itself. Complete failure of this unit occurs due to crumbling brushes of the collector, destruction of the dielectric layer between the plates, as well as due to a short circuit in the electrical circuit. If there is sparking inside the unit, the collector is worn out or the collector junction is damaged.

Brushes begin to spark if there is a gap in the area where they are in contact with the collector. This is preceded by a fall of the device, high load on the shaft when it jams, as well as a violation of the integrity of the solder on the winding leads.

Malfunction when the motor is running and shows the typical symptoms:

  • Sparking is the main sign of trouble.
  • Rumble and friction as the armature rotates.
  • Perceptible vibration during operation.
  • Swapping direction of rotation as armature travels less than a revolution.
  • Smell of melting plastic or intense heating of the housing.

What to do if the following problems occur?

The speed of the motor armature is kept constant. Malfunction may not appear at idle speed. Under load, friction is compensated by an increase in current flowing through the windings. If you notice deviations in the work of angle grinder, drill, starter, you must remove the voltage.

Continued use of the units may result in fire or electric shock to persons. First of all it is recommended to inspect the body of the product, to evaluate the wiring for integrity, the absence of melted parts and damaged insulation. Check the temperature of all parts to the touch. Try to rotate the armature by hand, it should move easily, without faltering. If mechanical parts are intact and not contaminated proceed to disassemble.

Diagnose the internal parts

Motor armature winding must be free of carbon deposits, dark spots, similar to the consequences of overheating. The surface of the contact parts and the gap area must be free of ashes. Small particles reduce motor power and increase current. Do not disassemble devices with the plug plugged in for safety reasons.

It is advisable to film the disassembly process to avoid complications during the reverse process. Or you can write down on a sheet of paper each step of your steps. Some wear and tear on brushes, lamellae is acceptable. But if scratches are found, it is necessary to find out the reason of their origin. Probably contributed to this by a crack in the housing, which can only be noticed under load.

Operation with an ohmmeter

Sparks can occur because of the loss of electrical contact in one of the lamellae. To measure the resistance it is recommended to put the feeler gauges on the side of the slats. Turn the motor shaft and observe the dial readings. The display should read zero. If even a few ohms slip through, it’s an indication of fouling. If there is an infinite value, it is judged about the break in the circuit.

Regardless of the results, you should then check the resistance between each neighboring slats. It must be the same for each measurement. If there are irregularities, all connections of the coils and the surface of the brushes should be inspected. The brushes themselves should have uniform wear and tear. If there are chips and cracks, they must be replaced.

The coils are connected to the core with wiring that may have peeled off. Solder is often not able to withstand the impact of falls. The starter current through the contacts can reach 50A, which leads to the burnout of poor quality connections. Visually determine the location of the damage. If no fault is detected, then measure the resistance between the lamella and the coil itself.

If you do not have an ohmmeter?

If you don’t have a multimeter, you will need a 12 volt power supply and a light bulb with the appropriate voltage. Any car enthusiast will have no problem with this set. Connect the plus and minus terminals to the plug of the electrical device. An incandescent lamp is placed in the gap. The result is observed visually.

Armature shaft rotated by hand, lamp lights up without brightness fluctuations. A defective motor is indicated if a fade is detected. Most likely an inter-turn fault has occurred. A complete loss of glow indicates a break in the circuit. Reason could be no contact of brushes, winding breakage or lack of resistance in one of the lamellae.

How to “revive” a defective device?

Repair of motor armature begins only when you are absolutely sure of the malfunction of the node. Scratches and chips on the blades are corrected by circular grinding of the surface. Carbon deposits and soot can be removed with electrical contact cleaners. Broken bearings could be pressed out and replaced with new ones. It is important to keep the shaft balanced during assembly.

Anchor and stator checker for electrical machines

Another device that can be used to verify the stator of an angle grinder is the PUNS 5 machine armature and stator verifier. The device has a light and sound alarm, allows to detect winding short circuits, open circuit, measure the insulation resistance of coils.

The device operates in two modes. “armature” and “stator. Mode change is made with a switch. The device is equipped with a handy device for mounting and fixing the tested motor. It consists of two feelers attached to the shaft. The claws move freely along the shaft, allowing you to change the distance between them and test motors of different sizes. Inspection carried out with two feeler gauges. Open circuit or short circuit in the stator winding is indicated by special red LEDs and sound signal. The test procedure is described in more detail in the instruction manual of the appliance.