How to check an electric motor with a multimeter: step by step instructions and recommendations. How to ring the motor windings: proven methods How to check the interturn circuit of the motor with a multimeter

direct current.

Measurement of the resistance of the stator windings to direct current is carried out in order to check the absence of breaks in the winding (for example, due to a violation of the integrity of the joints as a result of poor-quality soldering). When comparing the resistances of individual phases, you can determine:

1. Correspondence of the number of turns and wire section to the nominal data. In this case, the phase resistance is the same and corresponds to the catalog data;

2. The presence of a large number of closed turns in individual coils. The phase resistance in this case will be different.

Measurement of winding resistance to direct current is carried out by a direct current bridge P3043 (at the measurement limit of 0.330 Ohm). The measurement is carried out according to the schemes shown in Fig.3. The discrepancy between the measured resistance values ​​should not exceed 2%.

When measuring the resistance of windings connected to a deaf star (inside the machine) or a deaf triangle, measure the resistance at the terminals R C1-C2, R C2-C3, R C1-C3. With a "star", the phase value of the resistance R f \u003d R C1-C2 / 2; at the "triangle" R С1-С2 2/3. When measuring the resistance of windings with six output ends, the resistances are measured at the terminals R C1-C4, R C2-C5, R C3-C6.

The measurement results are entered in table 2.

Fig.3 Schemes for measuring the resistance of the stator windings to direct current with a direct current bridge.

a) with six winding leads;

b) with three leads and a star connection;

c) with three conclusions and a triangle connection.

Table 2.

The resistance of the motor windings to direct current.

A break in the winding at 6 output ends is determined by a megohmmeter. With a megohmmeter, it can be determined with a deaf star, touching in pairs all the terminals of the winding. With a blind triangle, this can be done with a DC bridge by measuring the ohmic resistance of the winding between the terminals. When measuring between C1-C3 (Fig. 3c) and C2-C3, we get the same values ​​\u200b\u200b(with a break between C1-C2), and between C1-C2 the resistance will be equal to the sum of the resistances of the other two phases.

2.4. Determination of the technical condition of the hull

phase-to-phase insulation of windings.

When measuring, a megohmmeter for a voltage of 500 or 1000V is used. Measure the insulation resistance of the windings relative to the case and relative to each other. The insulation resistance must be at least 0.5MΩ. Enter the data in table 3.

Table 3

Motor winding insulation resistance, MOhm

2.5 Determining the technical condition of the interturn

stator winding insulation.

For research, we present: an electric motor specially equipped with toggle switches on the terminal panel, with which faults are introduced into the winding, as well as 6 and 3-pin electric motors.

Table 4

The position of the toggle switches on the motor terminal board.

Note!

The toggle switch is on; - the toggle switch is off.

Determining the beginnings and ends of a winding with unmarked 6 output ends on alternating current.

On alternating current with 6 output ends, the induction method for checking the marking of the terminals is common (Fig. 5)

Fig.5 Scheme of the induction method for checking the marking of the stator terminals using an alternating current source.

H and K are the beginnings and ends of windings 1, 2, 3, respectively;

TV-regulating voltage transformer (LATR).

A megohmmeter determines whether the winding coil belongs to one phase. It is assumed that these conclusions are the beginnings, and the opposite ones are the ends of the windings. They take two arbitrary windings and connect them with the ends of the windings (Fig. 5 a). At the beginning of these windings, a reduced (1/5 - 1/6 Un) voltage of the AC network (50 - 75V) is supplied. If the first and second windings are connected by ends, then the voltmeter will not show voltage on the third winding. If the first and second windings are connected at opposite ends, then the voltmeter will show the voltage. Similarly, the conclusions of the third winding are marked.

Checking the electric motor is done with a tester in hand. Usually all contacts are called, the resistance value is measured. With a small level of knowledge about the internal structure of collector and asynchronous motors, it is possible to determine the breakdown. The protection system often fails. This is especially true for household appliances. Before checking the meat grinder motor, just wait a short time. In some models, there are temperature relays that do not allow the device to turn on until the motor has cooled down. Today we'll talk about how to check the electric motor.

What you need to check the electric motor

Of course, you will need a set of screwdrivers with various bits. The modern manufacturer protects its own products. Toaster, hair dryer or multicooker - to open the case, you will need more than one size and type of nozzles. Common screws for cross, TORX, asterisk and others are used. The part is non-standard, but with patience you will find the right head. Sets of bits of different configurations will do.

Most engines - no frills in the design of fasteners. Usually the heads are made for hexagons, crosses or slots. As for the brushes of the collector electric motors, the replacement is carried out using an improvised tool. It will take patience.

Motor type

If we are talking about a meat grinder or a vacuum cleaner, the engine inside is a collector. On the shaft there is a sectional drum for switching the rotor windings, on top of which the current collector slides. It looks like a copper-colored cylinder, the sidewall of which is divided into rectangles. Spare graphite brushes are included with the household appliance. And the maintenance of such an electric motor comes down to replacing them, periodically cleaning the copper drum. If graphite is packed between sections, sparking increases, a short circuit may occur between adjacent windings.

Collector motors are used because of the high torque at the start. Their speed is easily regulated by changing the cutoff angle. If two sharply different modes are required, this is provided by different stator windings. When spinning, the electric motor starts to work at full speed. Specific motors can differ significantly from typical ones. For example, they say that the collector motor has only two contacts, because the current flows continuously through the windings.

In practice, not only the washing machine engine has two switching options, controlled by a special relay (a sharp change in operating speed with the same supply voltage), but there are tachometer outputs. This is a sensor that measures shaft revolutions in order to correct the current cutoff angle. In addition, commutator motors are often equipped with circuits for extinguishing sparks and adjusting the speed when the load on the shaft changes:

1. Sparks are extinguished through varistors. Their resistance drops sharply with increasing voltage. Being connected in parallel to the brushes and closed to the motor housing, they close the circuit (right through the casing) during sudden power surges. The described property protects the windings from the vagaries of the power grid.
2. As for adjusting the rotation speed to the load on the shaft, it has long been noticed that with an increase in rotational resistance, the level of sparks rises. A special circuit monitors this and reduces the cutoff angle, as a result, the speed of the shaft increases again. This is how a fine adjustment is made for minor deviations in speed from the nominal value. This technique is often found in food processors, where the grater is able to chop cabbage or idle. As for, for example, vacuum cleaners, in the simplest models there is only spark suppression.

Let's talk about how to offhand understand whether a device with a collector or asynchronous motor is located nearby. As you might guess, the first ones make a lot of noise. However, in blenders it is not so noticeable. Collector motors are used where there is a large load at the start. We loaded the blender, turn it on. There is resistance to the rotation of the shaft, which must be overcome. For an asynchronous motor, the design would have to be significantly more complicated, and the weight and size characteristics would have suffered greatly. Therefore, mainly collector motors in household appliances.

This applies even to powerful kitchen hoods. Although in the simplest models there are asynchronous motors with a single winding. The specified type is found in fans. Finally, DC motors are often present in computer technology. The language does not dare to be called asynchronous, although they are similar in principle. The blade is so light that the induction induced by the permanent magnets is enough to spin. The launch comes from random air turbulences. A video has been posted on YouTube, where the field of coils is replaced by permanent magnets, and the fan (!) Is still spinning. In such engines, the malfunction is monitored by the continuity of the windings, there is nothing more to break here.

So, conclusions:

• In household appliances, for the most part, collector motors are used. Exception: fans, hair dryers, low-power cooker hoods.
• The commutator motor is distinguished by the presence of graphite brushes. The sectional brass drum gives this type. If these signs are absent, the motor is asynchronous.
• Maintenance of the collector motor is reduced to working with brushes and a sectional drum. In asynchronous, only windings and thermal fuses burn.

The beginning of the repair of the electric motor

Once the motor type has been determined, you can begin to determine the number of phases. By the way, industrial-type asynchronous motors are often made in powerful ribbed cylindrical housings - an additional key feature. The brushes are fragile, they try not to use commutator motors here. As for asynchronous, copper is not afraid (unlike graphite) of shaking, factories are equipped mainly with them. Raising the torque at the start and improving other characteristics, special design solutions are used. For example, the rotor winding is performed in two layers. The lower one works exclusively at the start, while the induction currents are of low frequency. When the shaft is untwisted, the auxiliary layer is turned off from the work process. Of course, the same thing happens with a decrease in speed.

A massive steel case usually indicates that the motor is asynchronous. Think: the dust in the workshop would have a negative impact on the quality of contact of the brushes with the surface. Although in vacuum cleaners the air flow is immediately used to cool the windings, do not forget that a thorough filtration is carried out. If you take the best Dyson models, the cleaning quality is such that the HEPA stages can not be changed during operation. We are talking about particles with a size of 5 microns. Conclusion - if the collector motor is already used in adverse conditions, special measures are taken.

Perhaps it is worth isolating the brushes from the room at all? But when the equipment is running, a lot of heat is generated. Forced cooling required. Otherwise, it would be extremely easy to determine the breakdown - the overheating protection circuits: relays and thermal fuses would constantly fail. Or the windings are on fire. Read the instructions in the papers. As a rule, there are a lot of instructions. Therefore, it is easy to determine what is broken.

If readers expected to find detailed instructions in the review on how to check the motor armature at home, it is possible that some individuals were upset. The authors believe that it is much more important to understand where to look for a malfunction. You can discuss with foam at the mouth how to check the engine of a washing machine, and at the same time not pay attention to the fact that the pressure switch has failed. And his testimony simply does not allow the equipment to start. Similarly, before checking the refrigerator motor, familiarize yourself at least approximately with the device of the start-up relay, which is responsible for the correct switching of the windings at the start and after the shaft accelerates. As for dialing issues, this is a short-lived matter. Much easier than winding a section on the rotor of an angle grinder collector motor.

DC motors are widely used. Especially in the automotive industry. They are necessary for the operation of power windows and wipers, are included in the car's cooling system, etc.

The reliability of the entire device depends on the quality and performance of such engines. On the site http://www.sbpower.ru/brands/allen-bradley you will find only the highest quality motors and other electrical products.

Checking the integrity of the windings

DC motors are called collector motors. Their performance can be checked using a device called a multimeter. All actions are performed in this order:

1. The tester enters the resistance measurement mode (Ohm). The probes are applied in pairs to the collector lamellas. If the engine is running, the readings will be the same.
2. For a running engine, the resistance will be infinitely high if you simultaneously attach the probes to the armature and the collector.
3. Motor failure may be due to a broken winding. Using the device, we check for the presence of these defects.
4. One probe touches the stator box, and the second is applied to the motor leads. A low value will indicate a malfunction.

There are other types of engine checks, but they are used by craftsmen who repair various appliances. At home, you can limit yourself to the method described above.

Other types of checks

You can check the health of the engine in other ways. There are special devices that allow you to check the armatures of DC motors. You need to attach the engine to a special prism of the device, and then plug it into the network. During the diagnostic process, you need to slowly turn the engine. An interturn short circuit is indicated by vibration and attraction of the interturn web to the groove.

In order to quickly check the engine, you can use special working stands. This is a special design, consisting of a DC source, an inverter, a digital voltmeter, a voltage comparator, an indicator light and a buzzer that signals a break.

The stand can be assembled independently, but this is advisable if you are engaged in the diagnosis and repair of DC motors. At home, to check, it is enough to use a simple tester, which can be purchased at any electrical store at an affordable price.

In a previous article, I talked about how to check, troubleshoot and troubleshoot commutator motors, which differ in that they have a brush-collector assembly. Now I will tell you how to check, troubleshoot and repair asynchronous electric motor, which is the most reliable and easiest to manufacture of all types of motors. They are less common in everyday life (in a refrigerator compressor or in a washing machine), but for that often in a garage or workshop: in machine tools, compressors, etc.

Repair or check do-it-yourself asynchronous electric motor will not be hard for most people. The most common failure in asynchronous motors is the wear of bearings, less often breakage or dampness of the windings.

Most faults can be identified by external inspection.

Before connecting or if the motor has not been used for a long time, it is necessary to check the insulation resistance of it with a megger. Or if there is no familiar electrician with a megohmmeter, then it does not hurt to disassemble it and dry the stator windings for several days for preventive purposes.

Before starting repairs electric motor, it is necessary to check the presence of voltage and the serviceability of the magnetic starters, thermal relay, connection cables and capacitor, if any, in the circuit.

Checking the electric motor by external inspection

Full inspection can be carried out only after disassembling the electric motor, but do not rush to disassemble immediately.

All work is carried out only after shutdown power supply, checking its absence on the electric motor and taking measures to prevent its spontaneous or erroneous switching on. If the device is plugged into an outlet, then just remove the plug from it.

If there are capacitors in the circuit, then their conclusions must be discharged.

Check before starting disassembly:

1. play in bearings. How to check and replace bearings read in this article.
2. Check paint coverage on the hull. Burnt or peeling paint in places indicates engine heating in these places. Pay special attention to the location of the bearings.
3. Check the paws fastening the electric motor and the shaft together with its connection with the mechanism. Cracks or broken legs must be welded.

After disassembling according to this instruction, you need to check:

May burn out as part of the winding, an interturn circuit will occur (in the picture on the left), and the entire winding (in the right picture). Despite the fact that in the first case the motor will run and overheat, it is still necessary to rewind the windings in any case.

How to ring an asynchronous electric motor

If nothing is revealed during the external examination, then it is necessary to continue the check using electrical measurements.

How to ring an electric motor with a multimeter

The most common in the household, the electrical measuring instrument is a multimeter. With its help, you can ring the integrity of the winding and the absence of a breakdown on the case.

In 220 volt motors. It is necessary to ring the starting and working windings. Moreover, the starting resistance will be 1.5 times greater than that of the working one. For some electric motors, the starting and working windings will have a common third terminal. Read more about this here.

For example, the motor from the old washing machine has three outputs. The greatest resistance will be between two points, including 2 windings, for example 50 ohms. If you take the remaining third end, then this will be the common end. If you measure between it and the 2nd end of the starting winding, you will get a value of about 30-35 ohms, and if between it and the 2nd end of the working winding, about 15 ohms.

In 380 volt motors, connected according to the star or triangle scheme, it will be necessary to disassemble the circuit and ring each of the three windings separately. Their resistance should be the same from 2 to 15 ohms with deviations of no more than 5 percent.

Definitely need to call all windings between themselves and on the case. If the resistance is not great to infinity, then there is a breakdown of the windings between themselves or on the case. Such motors must be put into winding rewinding.

How to check the insulation resistance of the motor windings

Unfortunately, can't check with a multimeter the value of the insulation resistance of the motor windings, this requires a 1000 volt megger with a separate power source. The device is expensive, but every electrician at work who has to connect or repair electric motors has it.

When measuring one wire from the megohmmeter is connected to the body in an unpainted place, and the second in turn to each winding terminal. Then measure the insulation resistance between all windings. If the value is less than 0.5 Megoma, the engine must be dried.

be careful, to avoid electric shock, do not touch the test clamps while measuring.

All measurements are taken only on de-energized equipment and for a duration of at least 2-3 minutes.

How to find an interturn circuit

The most difficult is the search for an interturn circuit, at which only a part of the turns of one winding is closed to each other. It is not always detected during an external examination, therefore, for these purposes, it is used for 380 Volt motors - an inductance meter. All three windings must have the same value. With an interturn circuit, the damaged winding will have a minimum inductance.

When I was in practice 16 years ago at the plant, electricians used a bearing ball with a diameter of about 10 millimeters to search for turn-to-turn short circuits in a 10 kilowatt asynchronous motor. They took out the rotor and connected 3 phases through 3 step-down transformers to the stator windings. If everything is in order, the ball moves in a circle of the stator, and in the presence of an interturn short circuit, it is magnetized to the place of its occurrence. The check should be short-term and be careful the ball can fly out!

I've been an electrician for a long time and I check for turn-to-turn shorts, unless a 380V motor starts to get very hot after 15-30 minutes of operation. But before disassembling, with the motor turned on, I check the amount of current it consumes in all three phases. It should be the same with a slight correction for measurement errors.

To find out the cause of the problem of the electric motor, it will not be enough just to inspect it, you need to carefully check it. You can quickly do this with an ohmmeter, but there are other ways to check. How to check the electric motor, we will describe below.

First, the test begins with a thorough inspection. In the presence of certain defects of the device, it can fail much earlier than the deadline. Defects may appear due to improper operation of the engine or its overload. These include the following:

• broken stands or mounting holes;
• the paint in the middle of the engine has darkened due to overheating;
• the presence of dirt and other foreign particles inside the motor.

The inspection also includes checking the markings on the motor. It is printed on a metal nameplate., which is attached to the outside of the engine. The label contains important information about the technical specifications of this instrument. As a rule, these are parameters such as:

• information about the manufacturer of the engine;
• model name;
• serial number;
• the number of revolutions of the rotor per minute;
• device power;
• a diagram of connecting the engine to certain voltages;
• a scheme for obtaining one or another speed and direction of movement;
• voltage - requirements in terms of voltage and phase;
• dimensions and type of case;
• description of the stator type.

The stator on the electric motor can be:

• closed;
• blown by a fan;
• splashproof and other types.

After inspecting the device, you can begin to check it and you need to do this starting with the engine bearings. Very often, electric motor malfunctions occur due to their breakdown. They are needed so that the rotor moves smoothly and freely in the stator. Bearings are located at both ends of the rotor in special niches.

For electric motors, the most commonly used types of bearings are:

• brass;
• ball bearings.

Some need to be equipped with grease fittings, and some are already lubricated during production.

Bearings should be checked as follows:

• place the engine on a hard surface and place one hand on top of it;
• turn the rotor with the other hand;
• try to hear scratching sounds, friction and uneven movement - all this indicates a malfunction of the device. A serviceable rotor moves calmly and evenly;
• we check the longitudinal play of the rotor, for this it needs to be pushed by the axis from the stator. Play is allowed up to a maximum of 3 mm, but not more.

If there are problems with the bearings, then the electric motor is noisy, they themselves overheat, which can lead to the failure of the device.

The next stage of verification is checking the motor winding for a short circuit on his body. Most often, a household motor will not work with a closed winding, because a fuse will burn out or a protection system will work. The latter is typical for ungrounded devices designed for a voltage of 380 volts.

An ohmmeter is used to check the resistance. You can check the motor winding with it in this way:

• set the ohmmeter to the resistance measurement mode;
• we connect the probes to the desired sockets (as a rule, to the common “Ohm” socket);
• select the scale with the highest multiplier (for example, R*1000, etc.);
• set the arrow to zero, while the probes should touch each other;
• we find a screw for grounding the electric motor (most often it has a hex head and is painted green). Instead of a screw, any metal part of the case can be used, on which the paint can be scraped off for better contact with the metal;
• we press the probe of the ohmmeter to this place, and press the second probe in turn to each electrical contact of the engine;
• Ideally the pointer of the measuring device should deviate slightly from the highest resistance value.

During operation, make sure that your hands do not touch the probes, otherwise the readings will be incorrect. The resistance value must be shown in million ohms or MΩ. If you have a digital ohmmeter, some of them do not have the ability to set the device to zero, for such ohmmeters the zeroing step should be skipped.

Also, when checking the windings, make sure that they are not short-circuited or broken. Some simple single-phase or three-phase electric motors are tested by switching the range of an ohmmeter to the lowest, then the needle goes to zero and a resistance measurement is made between the wires.

To make sure that each of the windings is measured, you need to refer to the motor circuit.

If the ohmmeter shows a very low resistance value, then it either exists, or you touched the probes of the device. And if the value is too high, then this indicates a problem with the motor windings, for example, about the gap. With a high resistance of the windings, the engine will not work at all, or its speed controller will fail. The latter most often concerns three-phase motors.

Checking Other Parts and Other Potential Problems

Be sure to check the starting capacitor, which is needed to start some models of electric motors. Basically these capacitors are equipped with a protective metal cap inside the motor. And to check the capacitor you need to remove it. Such an inspection may reveal signs of a problem, such as:

• oil leakage from the condenser;
• the presence of holes in the body;
• swollen capacitor case;
• unpleasant odors.

The capacitor is also checked with an ohmmeter. The probes should touch the terminals of the capacitor, and the resistance level should first be small, and then gradually increase as the capacitor charges with battery voltage. If the resistance does not increase or the capacitor is short-circuited, then most likely it is time to change it.

The capacitor must be discharged before retesting.

We proceed to the next stage of checking the engine: the rear of the crankcase, where the bearings are installed. In this place a number of electric motors are equipped with centrifugal switches, which switch start capacitors or circuits to determine the number of revolutions per minute. You also need to check the relay contacts for burntness. In addition, they should be cleaned of grease and dirt. The switch mechanism is checked with a screwdriver, the spring should work normally and freely.

The question often arises of how to check the electric motor after failure, as well as after repair, if it does not spin. There are several ways to do this: external inspection, a special stand, “ringing” of the windings with a multimeter. The last method is the most economical and versatile, but it does not always give the right results. For most constants, the winding resistance is practically zero. Therefore, an additional circuit for measurements is required.

Motor design

To quickly learn how to check an electric motor, you need to clearly understand the structure of the main parts. At the heart of all motors is two parts of the design: the rotor and the stator. The first component always rotates under the action of an electromagnetic field, the second is stationary and just creates this vortex flow.

To understand how to check the electric motor, you will need to disassemble it at least once with your own hands. Different manufacturers have different designs, but the principle of diagnosing the electrical part so far remains unchanged. There is a gap between the rotor and the stator, in which small metal chips can accumulate when the housing is depressurized.

Bearings, when worn, can give overestimated current values, as a result of which the protection will be knocked out. When dealing with the question of how to check the electric motor, do not forget about mechanical damage to moving parts and boron, where the contacts are located.

Difficulties in diagnosis

Before checking the electric motor with a multimeter, you should conduct an external inspection of the housing, the cooling impeller, check the temperature by touching the metal surfaces with your hand. A heated case indicates an overcurrent due to problems with the mechanical part.

You will need to analyze the condition of the internals of the boron, check the tightening of the bolts or nuts. With an unreliable connection of current-carrying parts, the failure of the windings can occur at any time. The surface of the engine must be free of dirt and moisture inside.

If we consider the question of how to check the electric motor with a multimeter, then several nuances must be taken into account:

• In addition to the multimeter, you will need clamps for non-contact measurement of the current passing through the wire.
• A multimeter can only measure slightly high resistances. To check the condition of the insulation (where the resistance is from kOhm to MΩ), a megohmmeter is used.
• To draw conclusions about the suitability of the motor, you will need to disconnect the mechanical components (reducer, pump, and others), or you need to be sure that these components are in full working order.

Switching equipment

To start the rotation of the windings, a board or relay is used. To begin to deal with the question of how to check the motor winding, you need to unhook the supply chain. Through it, the elements of the control board can “ring”, which will introduce an error into the measurements. With the wires folded back, you can measure the incoming voltage to be sure that the electronic circuit is working.

In household appliances, a design with a starting winding is often used, the resistance of which exceeds the value of the operating inductance. When measuring, take into account the fact that current-collecting brushes may be present. Carbon deposits often appear at the point of contact with the rotor, after cleaning it, it is necessary to restore the reliability of the brushes during rotation.

In washing machines, small-sized motors with one working winding are used. The whole essence of diagnostics comes down to measuring its resistance. The current is measured less frequently, but by taking characteristics at different speeds, conclusions can be drawn about the health of the motor.

Electrical Diagnosis Details

Consider how to check the health of the electric motor. First of all, inspect the contact connections. If there is no visible damage in them, then they open the junction of the wires with the engine and turn them off. It is desirable to determine the type of motor. If it is a collector, then there are lamellas or sections at the place where the brushes fit.

It is required to measure the resistance between each adjacent lamellas with an ohmmeter. It must be the same in all cases. If short-circuited sections or their breakage are observed, then the motor tachometer must be replaced. If you “ring out” the rotor coil itself, then 12 V of the multimeter may not be enough. An external power supply is required to accurately assess the condition of the winding. It can be a block from a PC or a battery.

To measure small resistance values, a resistor with a known value is installed in series with the measured winding. It is enough to choose a resistance of about 20 ohms. After power is supplied from an external source, they are measured on the winding and resistor. The resulting value is obtained from the formula R1 = U1*R2/U2, where R2 is the resistor, U2 is the voltage drop across it.

Diagnostics of asynchronous motors

The difference in resistance readings between adjacent collector plates is allowed no more than 10%. When an equalizing winding is provided in the design, the operation of the motor will be normal with a difference in values ​​​​of 30%. Multimeter readings do not always give an accurate prediction of the condition of the washing machine engine. In addition, an analysis of the operation of the motor on a test bench is often required.

Checking the direct drive motor

If we consider the question of how to check the electric motor of the washing machine, then the type of connection of the drum to the shaft should be taken into account. This depends on the type of construction of the electrical part. The windings are called with a multimeter and conclusions are drawn about their integrity.

The performance test is carried out after replacing the Hall sensor. It is he who fails in most cases. After ringing the windings with their integrity, experienced craftsmen recommend connecting the motor directly to a 220 V network. As a result, uniform rotation is observed to change its direction, you can replug the plug in the outlet by turning it with other contacts.

This simple method helps to identify a common problem. However, the presence of rotation does not guarantee normal operation in all modes that differ during spinning and rinsing.

Diagnosis sequence

First of all, it is recommended to immediately pay attention to the condition of the brushes and wiring. Nagar on current-carrying parts indicates abnormal engine operating modes. The current collectors themselves must be smooth, without chips or cracks. Scratches also lead to sparking, which is detrimental to motor windings.

In washing machines, the rotor often warps, because of this, chipping or breaking of the lamellae occurs. The control board constantly monitors the position of the rotor through or tachogenerator, adding or decreasing the voltage applied to the working winding. From here there is a strong noise during rotation, sparking, violation of operating modes during the spin cycle.

This phenomenon can only be noticed during the spin cycle, and the washing mode is stable. Diagnostics of the operation of the machine does not always go through an analysis of the state of the electrical part. Mechanics may be the cause of incorrect operation. Without load, the engine can spin quite evenly and stably gain momentum.

If it still knocks out protection?

After the measurements taken with floating faults, it is not recommended to connect to the network for verification. You can permanently disable the motor without suspecting a problem. How to check the motor winding with a multimeter, the service center master will tell you by phone. Under his guidance, it will be easier to determine the type of construction and the procedure for diagnosing a faulty washing machine.

However, often even experienced craftsmen cannot cope with the repair of complex cases when the malfunction is floating. To check in the service, you need to use a washing machine, mechanical components are crucial. Motor shaft misalignment is a special case of drum rotation problems.

Single-phase motors are electrical machines of small power. In the magnetic circuit of single-phase motors there is a two-phase winding, which consists of the main and starting windings.

The most common motors of this type can be divided into two groups: single-phase motors with a starting winding and motors with a run capacitor.

For motors of the first type, the starting winding is switched on through the capacitor only at the moment of starting, and after the motor has developed a normal rotation speed, it is disconnected from the network, after which the motor continues to operate with one working winding. Capacitor capacity is usually indicated on the nameplate of the motor and depends on its design.

For single-phase asynchronous motors with a running capacitor, the auxiliary winding is connected permanently through the capacitor. The value of the working capacitance of the capacitor is determined by the design of the engine.

If the auxiliary winding of a single-phase motor is starting, it will only be connected during the start. If the auxiliary winding is a capacitor winding, then its connection will occur through a capacitor. And it stays on while the engine is running.

In most cases, the starting and working windings of single-phase motors differ both in the cross section of the wire and in the number of turns. The working winding of a single-phase motor always has a larger wire section, and therefore its resistance will be less.

The winding with less resistance is the working winding.

If the engine has 4 outputs, then by measuring the resistance between them, it can be determined that the lower resistance is lower for the working winding, and, accordingly, the starting resistance is higher.

Connecting everything is pretty easy. 220v is supplied to thick wires. And one tip of the starting winding, for one of the workers, does not matter which one, the direction of rotation does not depend on it. It also depends on how you insert the plug into the socket. The rotation will change from connecting the starting winding, namely, by changing the ends of the starting winding.

In the case when the motor has 3 outputs, the measurements will look like this, for example - 10 ohms, 25 ohms, 15 ohms. By measuring it is necessary to find the tip from which the readings, with the other two, will be 15 ohms and 10 ohms. This will be one of the network wires. The tip with 10 ohms is also a network and the third 15 ohm will be the starting one, it is connected to the second network through a capacitor. In this case, to change the direction of rotation, you need to get to the winding circuit.

The case when measurements, for example, show 10 ohms, 10 ohms, 20 ohms. is also one of the varieties of windings. for example in some washing machines and not only. In such cases, the working and starting windings are the same (according to the design of three-phase windings). In this case, it does not matter which winding will play the role of a working winding, and which starting winding. Connection is also made through a capacitor.

Types of electric motors

The most common electric motors are;

Asynchronous three-phase squirrel-cage motor

Asynchronous three-phase motor with squirrel-cage rotor. Three motor windings are laid in the stator slots;
- asynchronous single-phase motor with a squirrel-cage rotor. It is mainly used in household electrical equipment in vacuum cleaners, washing machines, hoods, fans, air conditioners;
- collector DC motors are installed in the electrical equipment of the car (fans, power windows, pumps);
- AC commutator motor finds application in electric tools. Such tools include electric drills, grinders, perforators, meat grinders;
- an asynchronous motor with a phase rotor has a fairly powerful starting torque. Therefore, such motors are installed in hoist drives, cranes, elevators.

Winding insulation resistance measurement

To test the motor for insulation resistance, electricians use a megger with a test voltage of 500 V or 1000 V. This device measures the insulation resistance of motor windings rated for an operating voltage of 220 V or 380 V.

For electric motors with a rated voltage of 12V, 24V, a tester is used, since the insulation of these windings is not designed for testing with a high voltage of 500V megger. Usually, the test voltage is indicated in the passport for the electric motor when measuring the insulation resistance of the coils.

Insulation resistance is usually checked with a megger

Before measuring the insulation resistance, you need to familiarize yourself with the connection diagram of the electric motor, since some star connections of the windings are connected by a midpoint to the motor housing. If the winding has one or more connection points, "delta", "star", single-phase motor with starting and working winding, then the insulation is checked between any connection point of the windings and the housing.

If the insulation resistance is significantly less than 20 MΩ, the windings are disconnected and checked each separately. For a whole motor, the insulation resistance between the coils and the metal case must be at least 20 MΩ. If the motor has been operated or stored in damp conditions, then the insulation resistance may be below 20 MΩ.

Then the electric motor is disassembled and dried for several hours with a 60 W incandescent lamp placed in the stator housing. When measuring insulation resistance with a multimeter, set the measurement limit to the maximum resistance, to megohms.

How to ring an electric motor for a winding break and an interturn short circuit

The turn-to-turn short circuit in the windings can be checked with a multimeter on ohms. If there are three windings, then it is enough to compare their resistance. The difference in the resistance of one winding indicates an interturn short circuit. The turn-to-turn short circuit of single-phase motors is more difficult to determine, since there are only different windings - this is the starting and working winding, which has less resistance.

There is no way to compare them. It is possible to identify the interturn short circuit of the windings of three-phase and single-phase motors with measuring clamps, comparing the winding currents with their passport data. With an interturn circuit in the windings, their rated current increases, and the starting torque decreases, the engine starts with difficulty or does not start at all, but only buzzes.

Checking the motor for open circuit and interturn circuit of the windings

It will not work to measure the resistance of the windings of powerful electric motors with a multimeter, because the cross section of the wires is large and the resistance of the windings is within tenths of an ohm. It is not possible to determine the difference in resistance, with such values ​​​​with a multimeter. In this case, the health of the electric motor is best checked with current clamps.

If it is not possible to connect the electric motor to the network, the winding resistance can be found by an indirect method. A series circuit is assembled from a 12V battery with a 20 ohm rheostat. Using a multimeter (ammeter), a current of 0.5 - 1 A is set with a rheostat. The assembled device is connected to the winding under test and the voltage drop is measured.

Electric motor continuity and insulation resistance

A smaller voltage drop across the coil will indicate an interturn short circuit. If you want to know the resistance of the winding, it is calculated by the formula R \u003d U / I. A motor failure can also be determined visually, on a disassembled stator, or by the smell of burnt insulation. If the place of the break is visually detected, it can be eliminated, the jumper soldered, well insulated and laid.

The measurement of the winding resistance of three-phase motors is carried out without removing the jumpers on the connection diagrams of the "star" and "delta" windings. The resistance of the coils of collector electric motors of direct and alternating voltage is also checked with a multimeter. And with their high power, the check is carried out using the accumulator - rheostat device, as indicated above.

The winding resistance of these motors is checked separately on the stator and rotor. On the rotor, it is better to check the resistance directly on the brushes by turning the rotor. In this case, it is possible to determine the loose fit of the brushes to the rotor lamellas. Eliminate carbon deposits and irregularities on the collector lamellas by grinding them on a lathe.

It is difficult to do this operation manually, you can not eliminate this malfunction, and the sparking of the brushes will only increase. The grooves between the lamellas are also cleaned. In the windings of electric motors, a fuse, a thermal relay can be installed. If there is a thermal relay, check its contacts and, if necessary, clean them.

Today we will discuss how to ring an electric motor with a multimeter. A screwdriver-indicator is suitable for those who know how to use it. One caveat: with the help of a tester, we will evaluate the parameters, distinguish the starting winding from the working winding by the resistance value (in the first case, the value will be twice as high). The indicator screwdriver is miniature, convenient, you will acquire the ability to use it, if necessary, by paying 30 rubles you will find a new one.

Motor device

There are many types of engines. Composed by a moving part - a rotor - a fixed part - a stator. First of all, let's see where the copper wire is wound. There are three answer options:

1. Coils on the rotor only.
2. Coils on the stator only.
3. On the movable and fixed parts of the winding.

Otherwise, ringing an asynchronous electric motor will be no more difficult than a collector one. And vice versa. The difference is limited to the principle of operation, without affecting the methodology for assessing the performance of the structure. To correctly ring the electric motor, stop disassembling the features.

Motor rotor

In this and the next subheading, we will teach you how to ring a three-phase electric motor. If there are coils (regardless of the number) on the rotor, we look at the design of the current collector. There are at least two answers.

Graphite brushes

We see the rotor drum, equipped with pronounced sections. Current collectors are graphite brushes. Collector motor. You need to ring all sections. The coil leads are opposite sections of the circle.

We take a tester, we begin to evaluate the resistance one by one: in each case, the answer (in ohms) is the same plus or minus the error. When fixing a break, cleaning the drum does not help. The fact of infinite resistance or short circuit indicates: the coil burned out. In some engines, the coil resistance is close to zero.

They told me what to do in this case. Take a normal Krona 12 volts, connect the rotor coil in series with a low-resistance resistance (20 ohms). Using a tester, measure the voltage drop across the coil, additional resistor, using the proportion, calculate the value (R1 / R2 \u003d U1 / U2). Please note that the resistor is high-precision (E48 series or higher), so that the calculations have a small error. It is possible to measure relatively small resistances.

Please note: the current reaches 0.5A at a power of 7W. Instead of a battery, it is better to take a computer power supply or a battery.

Continuous rings

The current collector is made in the form of one or more continuous rings. It indicates eloquently: a synchronous motor (the number of phases by the number of sections), or an asynchronous motor with a phase rotor. Actually, this is not the case, because we were going to ring the electric motor with a tester, we will be too lazy to determine the purpose of the device. We look at the number of rings: the number fits within the limits of 1 - 3. The latter means: a three-phase motor. We start calling.

The windings are connected in a star, as a result, the resistance between each two contacts is equal. If you have equipment on hand to create a voltage of 500 V, you should ring the electric motor with a megohmmeter on the case. The standard insulation value is 20 MΩ. Please note: windings may not pass the test. With a 12 volt motor, such actions should not be taken. As a result, with a fully serviceable rotor, equal resistance will be obtained between the contacts. If a short to ground is detected, check if it is a technical solution to create a system with a solidly grounded neutral.

It's time to mention that for such a system, the power supply method is typical for voltages below 1 kV. However, with resonant compensation (if it is possible to find an engine in nature), something similar can be used. On the nameplate with the marking, you can quickly resolve the issue (neutral output to the housing).

Collector brushes are more often located perpendicular to the surface of the drum, while they are pressed against the current collectors at a certain angle. The question arises - where is the neutral. Does not go to the body - do not use in the circuit. Often found at voltages above 3 kV. Here the neutral is isolated, the currents go through the phase, where in this case there is zero (or a negative value).

In high voltage circuits, the common wire can be grounded through the arcing reactor. When one phase is short-circuited to ground, a parallel circuit is formed between the line capacitance and the reactor inductance. Actually, the type of impedance gave the name to the device (the imaginary, reactive part of the resistance). At industrial frequency, the resistance of the circuit is close to infinity, as a result, the break is blocked until the arrival of the repair team.

The rotor is often referred to as the armature.

motor stator

After calling the rotor of the electric motor, take care of the stator. Detail of a simpler design. If we have a generator in front of us, part of the exciting windings, in the general case, you just need to find the resistance of each. Windings are starting only single-phase circuits. The coil resistance will be higher. Let's say there are three contacts, then the distribution between them is as follows:

• The common wire of both windings, where zero (ground) is applied.
• Phase input of the working coil.
• The end of the starting winding, where 230 volts is supplied, bypassing the capacitor.

The difference is made by the value of the resistance: between the phase inputs, the value is greater, therefore, the remaining end is the neutral wire. Further division is carried out as described above. The resistance of the starting coil is the largest (the difference between zero and this contact), the remaining ends will indicate the working winding. The value of the active part of the impedance is reduced, reducing thermal losses. Please note: there are also models of electric motors for 230 volts, where both windings are considered to be working. The difference in resistance between them is small (less than two times).

For three-phase motors, the stator windings are made for a different number of poles, always equivalent. Strict symmetry is practiced. The association is carried out according to the star scheme. In high power collector motors, additional (additional) ones can be placed between the poles of the main coil. They are wound in one layer, therefore they show more resistance. Designed to compensate for the reactive power of the armature. It is clear that the number of additional poles is equal to the number of main ones. The difference is limited by geometric dimensions.

The core of the additional poles is made with an overlap (laminated design) to reduce eddy currents. Similar to the rotor, it will not be enough to ring a three-phase electric motor with a multimeter, you should also measure the insulation of the case (typical value 20 MΩ).

Additional engine design

Often the composition of engines is replete with additional elements that optimize the work, performing a protective, different function. Varistors should be included here. Resistors connecting each brush to the body, with a sharp increase in voltage, close the spark. Extinguishing is in progress. Phenomena such as circular fire on the collector lead to premature equipment failure.

The phenomenon is observed as a result of the occurrence of back-EMF. The generation mechanism is quite simple: when the current changes in the conductor, a force is formed that counteracts the process. In the process of moving to the next section, the phenomenon causes the appearance of a potential difference between the brush and the non-working part of the collector. At voltages above 35 volts, the process causes ionization of the gap air, which is observed in the form of a spark. At the same time, the noise characteristics of the equipment deteriorate.

This phenomenon, however, is used to monitor the constancy of the speed of rotation of the shaft of the collector motor. The level of sparking is determined by the number of revolutions. When the parameter deviates from the nominal value, the thyristor circuit changes the voltage cutoff angle in the desired direction in order to return the shaft speed to the nominal one. Such electronic boards are often found in household food processors or meat grinders. The composition of the engine is as follows:

Electrical engine

1. Thermal fuses. The response temperature is chosen to protect the insulation from burnout and destruction. The fuse is fixed on the motor housing with a steel shackle, or is hidden under the winding insulation. In the latter case, the conclusions stick out, you can easily ring with a multimeter. It is easier to trace, with the help of a tester, an indicator screwdriver, which pins of the connector the protection circuit goes to. In the normal state, the thermal fuse gives a short circuit.
2. Temperature relays are installed instead of frequency fuses. Normally open or closed. The latter type is more commonly used. A brand is written on the body, you can find the corresponding type of element on the Internet. Then proceed according to the information found (type, resistance, response temperature, position of the contacts at the initial moment of time).
3. On the engines of washing machines, speed sensors and tachometers are often installed. In the first case there are three conclusions, in the second - two. The principle of operation of Hall sensors is based on the change in the potential difference in the transverse direction of the plate, through which a weak electric current flows. Accordingly, the two extreme outputs are used to supply power, they should give a short circuit (small resistance), while the output can only be checked under the influence of a magnetic field in operating mode. To do this, you need to supply power according to the electrical wiring. We recommend downloading the technical information (data sheet) for the Hall sensor present in the electric motor. Other options have been devised. You can measure the power with a tester while the washing machine is on. We believe readers understand the dangers of manipulation. It would be better to remove the electric motor, supply power separately, only to the Hall sensor. Then it all depends on the design. If the magnet is permanent on the rotor, it is enough just to rotate the axis by hand so that pulses appear at the output of the Hall sensor (fixed by the tester). Otherwise, you will need to remove the sensor. Enlisting the help of a permanent magnet, the performance is checked. The Hall sensor as part of the electric motor is usually used to control the speed of rotation.

Now readers know how to ring an electric motor with a multimeter, the review ends. A number of specific devices can be continued indefinitely. The main thing is to ring the motor winding, the motor usually costs more than other parts. We do not take the case when the Hall sensor is priced at 4,000 rubles. We are sure that readers will be able to supplement the recommendations. But enter into a position - it is impossible to embrace the immensity ... within one review.