How to check an electric motor at home. How to test a three-phase motor with a tester

How to check an electric motor, their windings for integrity. How to check 380 volts with a multimeter

It is easier to work when the electrical supply circuit of the house is properly grounded, we will show that there is always a way out. Let us explain how to understand where the phase is, and how to find out where zero is. Grab your favorite M890S! Let's see how to determine the phase and zero with a multimeter.

The simplest methods for finding the phase, zero with a multimeter

A properly organized ground loop at home eliminates problems. First, the PEN insulation is yellow-green. It is impossible to confuse with the brown (red) phase, blue neutral. It happens that the wiring is laid, violating the requirements, the colors are mixed up, there are none at all (aluminum cable). We search for a phase with a multimeter using a simple algorithm:

Let's say the apartment has three wires: phase, zero, ground.
We put the multimeter on the AC voltage range of 750 volts, we begin to test the wiring in pairs.
Between the phase and any other wire there will be 230 volts (rms), the ground-neutral jumper gives approximately 0.

multimeter

The drive shield has at least five wires, three phases. The further process is determined by the imagination of local electricians. Good craftsmen hang stickers A, B, C indicating the location of the phases. Grounding is yellow-green, neutral is often blue.

Between adjacent phases, the voltage is 380 (400) volts. High-rise apartments are sometimes supplied with two phases. Electric stoves with a power above 10 kW try to share consumption. Reduced wiring requirements. We advise you to immediately take a marker, mark the insulation with the desired colors. A house deprived of grounding usually receives two wires: phase, neutral. The substation transformer drives three phases. How much will be in the apartment, you should find out.

Problems will begin when there is no wire marking, the phase comes alone. Between dangerous wires, the voltage will be ... zero!

Two wires carry a phase, one neutral, they forgot to lay the ground. There is a round zero between the supply wires, when evaluating the neutral wire, we get 230 volts. The situation looks like the phase conductors have become neutral and zero. Messed up when laying - what can you do? It is required to look for an additional source of support. An indicator screwdriver will do.
Two wires of one phase, the second pair - grounding, neutral. In pairs they will show zero, crosswise - 230 V. Use a reference point.

There is no probe screwdriver, enlisting the help of a tester no matter how you call the wiring, the problem will remain. Requires a reference source that is guaranteed to be grounded. Suitable:

Due to the variety of methods, unreliability, it is recommended to conduct tests before starting serious work. Measure the potential between the indicated landmarks, the phase of the outlet. Is the distance between the landmark, destination large? We take an extension. Especially good is the personal computer power filter, equipped with a characteristic illuminated button. The phase is on the left, the left pin of the plug (depending on which side to turn) is marked with a marker.

Then we call with an outlet (without power, of course), make a mark on the right side. We explain, you can do without it, with an electrician it is better to put aside jokes. It remains to find the phase using the M890C. We set the range above 380 volts (between two phases), we begin to measure the potential difference between the terminals and the shield. We believe that the further algorithm is clear.

Correctly measure phase consumption

Let's measure the load of the phases. To put the right machines, observe uniform consumption. According to the rules of a three-phase network, each branch is loaded equally, avoiding distortions on the supplier's side. Let's evaluate which phases are included in the apartment. It's easier to look into the access shield. An inexperienced person must stop trying to climb there. It's easy to get an electric shock.

The house is old - in plain sight you will see a large steel plate, which is clearly connected to the body. Meaning - neutral. The house is powered by a three-phase voltage of 380 volts. Each apartment is supplied more often with one phase. We observe a triple of clamps in addition to the ground terminal. Look where the wires go: automatic machines, knife switches (according to the bill of apartments). A typical number of site neighbors of three simplifies the task of analysis.

Now we know the method of finding the phase with a multimeter, we can safely (with caution, observing safety measures) poke the probes. Take the trouble to set the correct range, do not burn the device. Confirm or refute the assumptions with measurements. There are two phases - load each equally. Examine the junction boxes found in most old houses under the ceiling (large round holes in the wall). Having turned off the supply of the apartment, armed with a tester, understand where and what goes. Use a radical method - chop off one cork, see where the power has gone.

The load of the two phases is uneven - correct. It is better to do for machines and traffic jams, which will have a positive effect on reducing the cost of switchboard equipment. In conclusion on this topic, let us say that the rules of work provide for the implementation of such events by at least two persons. One is sure to insure and is ready to cut off the power supply, cut off the current-carrying core or kick the person suffering from an electric shock from the dangerous territory with his foot.

The power supply scheme of the apartment in two phases

How to measure three-phase voltage with a multimeter

In this section, we will rather focus on the specifics of three-phase networks. Most multimeters can measure voltages up to 750 volts AC, which is enough to work with serious industrial networks. Each house is supplied from three phases. And what is called neutral in the industry, we call the neutral wire.

Enterprise networks are laid in two types:

Mechanisms with isolated neutral do not use a neutral wire. Inside the loads, the phases are equalized, the currents flow through the same wires, of which there are three in total. Tired of looking for a neutral - the line is missing. Three phase wires, relative to the ground will show a voltage of 230 volts, between themselves - 380.
The grounded neutral represents the neutral wire. Marked with the letter N on the boxes. It is useful to look at the circuit diagrams of industrial devices shown on the case. Helps to understand the layout.

Having mastered the techniques for working with three-phase voltage, everyone will be able to better understand the electrical wiring of a multi-storey building. Where four wires rise from under the shield: three phases and a neutral.

Car phase

Electrical networks help many objects. The car is considered a relatively simple device. The basis of the supply is a 12 volt battery (actually - 14.5 V), a generator, the output voltage level of which is regulated according to speed variations. The voltage after rectification is suitable to feed the battery of the on-board network. The generator shaft is activated by the battery through a special control device.

Three-phase circuit Larionov

The Larionov phase circuits rectified by a diode bridge feed the car. popular technique today. There are six diodes. The phases merge by mechanical union after straightening by a single line. Provides maximum power. Sensitive auto components (on-board computer) additionally rectify unstable current. To extend the life of the device.

Next, the voltage goes to consumers. Wipers, display system, lighting, ignition. The on-board computer may issue a coded message: it's time to check the phase sensor. An element whose work uses the Hall effect determines the position of the engine camshaft. Washing machines are equipped with similar ones, evaluating the rotation speed. Auto determines the angular position of the shaft. The sensor produces pulses, evaluating the parameters of which the computer will receive the necessary information.

The car is stuffed with sensors. Power is supplied to two terminals, the third generates a signal. To check, let's look at the diagram: the location of the nodes. Then let's take a closer look at the call. When simulating the conditions of pulse formation, use a permanent magnet.

The question of how to determine the phase and zero with a multimeter on a car disappears. The body of the car serves as a support - the mass. Of course, the generator only works when the engine is running. Inside the apartment we are looking for a phase and zero, here the mass is given a priori. Broken insulation can be caused (for example, rectifier bridge diodes). On a car, it's easier than ever to measure three phases with a multimeter. The effective value is indirectly said. About 20 volts (taking into account the losses of a non-ideal bridge).

Multimeter user errors

Chinese multimeters are set to work even if the probes are incorrectly placed. Break the appliance by accident beware. Avoid the method: plug the black wire into the high current measurement connector, the red one in its place. Try to measure the alternating voltage of a high-voltage line - repair is guaranteed. Wrong ranges must not be applied. Forget trying to measure AC voltage using a DC scale. The phase check will be the last in the life of the multimeter.

The device is disabled by a large voltage of alternating polarity. Others (for example, incorrect polarity of the probes) are not so scary.

vashtechnik.ru

How to check an electric motor with a multimeter: step by step instructions and recommendations

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, the voltage drop across the winding and resistor is measured. 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

Industrial washing machines can use powerful three-phase electric motors. Their rotor is often made in the form of typesetting plates with a magnetic core. Phase windings are often fixed and located in the stator.
It is much easier to check such a motor with a multimeter. With an ohmmeter, you need to ring the resistance of each winding. It must be the same. Do not forget to check the breakdown on the body by measuring the resistance to the body. However, it is more reliable to check the insulation with a megohmmeter.

Answering the question of how to check the windings of an electric motor with a tester, it should be noted that "phase imbalance" in an asynchronous motor is not allowed. The resistance difference should not exceed one ohm. Otherwise, the current at a lower inductance increases, which leads to burning of the winding.

If the DC motor

In such motors, the winding resistance is very small and measurements are carried out using two instruments. At the same time take readings from the ammeter and voltmeter. A battery with a voltage of 4-6 V is selected as a source. The resulting value is determined by the formula R \u003d U / I.

All available resistances of the armature windings are checked, the values \u200b\u200bof the collector plates are measured. All multimeter readings must be equal. From this comparison, conclusions can be drawn on how to check the armature of an electric motor.

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 a Hall sensor 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.

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How to ring the electric motor for integrity?

With the help of a multimeter and several devices, without really understanding the principle of operation of electric motors, you can check:

Winding insulation test

Regardless of the design, the motor must be checked with a megger for insulation breakdown between the windings and the housing. Testing with a multimeter alone may not be enough to detect insulation damage, so high voltage is used.

megohmmeter for measuring insulation resistance

The electric motor passport must indicate the voltage for testing the insulation of the windings for dielectric strength. For motors connected to a 220 or 380 V network, 500 or 1000 Volts are used when checking them, but in the absence of a source, you can use the mains voltage.

asynchronous motor passport

The insulation of the winding wires of low-voltage motors is not designed to withstand such overvoltages, therefore, when checking, you need to check the passport data. Sometimes, for some electric motors, the output of the star-connected windings can be connected to the housing, so you should carefully study the connection of the taps when making a check.

Checking the windings for open circuit and interturn circuit

To ring the windings for an open, you need to switch the multimeter to ohmmeter mode. An interturn short circuit can be detected by comparing the winding resistance with passport data or with measurements of symmetrical windings of the motor under test.

It must be remembered that for powerful electric motors, the cross section of the winding wires is large enough, so their resistance will be close to zero, and ordinary testers do not provide such measurement accuracy in tenths of an ohm.

Therefore, you need to assemble a measuring device from a battery and a rheostat, (approximately 20 ohms) setting a current of 0.5-1A. Measure the voltage drop across a resistor connected in series to the battery circuit and the measured winding.

For reconciliation with passport data, you can calculate the resistance using the formula, but you don’t have to do this - if the windings are required to be identical, then it will be enough to match the voltage drop across all measured outputs.

Measurements can be made with any multimeter

Digital multimeter Mastech MY61 58954

Below are the algorithms for checking electric motors, in which the necessary condition for operability is the symmetry of the windings.

Checking asynchronous three-phase motors with a squirrel-cage rotor

For such motors, only stator windings can ring, the electromagnetic field of which in the short-circuited rotor rods induces currents that create a magnetic field that interacts with the stator field.

Malfunctions in the rotors of these electric motors are extremely rare, and special equipment is needed to detect them.

motor rotor

To check a three-phase motor, you need to remove the terminal cover - there are terminals for connecting windings that can be connected in a "star" type

or "triangle". You can make a call without even removing the jumper -

it is enough to measure the resistance between the phase terminals - all three ohmmeter readings must match.

If the readings do not match, it will be necessary to disconnect the windings and check them separately. If the calculated resistance of one of the windings is less than that of the others, this indicates the presence of an interturn short circuit, and the motor must be rewound.

Checking capacitor motors

To test a single-phase asynchronous motor with a squirrel-cage rotor, by analogy with a three-phase motor, it is necessary to ring only the stator windings.

But single-phase (two-phase) electric motors have only two windings - working and starting.

The resistance of the working winding is always less than that of the starting

Thus, by measuring the resistance, it is possible to identify the conclusions if the plate with the diagram and symbols is overwritten or lost.

Often, for such motors, the working and starting windings are connected inside the housing, and a general conclusion is drawn from the connection point.

The affiliation of the conclusions is identified as follows - the sum of the resistances measured from the common tap must correspond to the total resistance of the windings.

Checking commutator motors

Since AC and DC collector motors have a similar design, the continuity algorithm will be the same.

First, check the stator winding (in DC motors, it can be replaced by a magnet). Then they check the rotor windings, the resistance of which should be the same, by touching the collector brushes with the probes, or opposite contact terminals.

It is more convenient to check the rotor windings at the brush terminals by turning the shaft, ensuring that the brushes are in contact with only one pair of contacts - in this way, burning can be detected at some contact pads.

Checking motors with a phase rotor

An asynchronous motor with a phase rotor differs from a conventional three-phase electric motor in that the rotor also has phase windings,

connected like a star

which are connected by means of slip rings on the shaft. To check the rotor windings, you need to find the conclusions from these rings, and make sure that the measured resistances match. Often such motors are equipped with a mechanical system for turning off the rotor windings when revving, so the lack of contact may be due to a breakdown in this mechanism.

The stator windings are checked as in a conventional three-phase motor.

Photos borrowed from the site http://zametkielectrika.ru

infoelectric.ru

How to check the phase

When performing maintenance work on apartment electricians, installing sockets, lighting switches, or carrying out minor repairs, it often becomes necessary to determine the phase and zero. If a person has some knowledge of the basics of electrical engineering, then it will be quite easy for him to find the phase and zero. But what if you don't have these skills? The search for phase and zero is not such a complicated process as it might seem at first glance. But, first of all, you need to decide what it is.

Our entire energy system is three-phase, including low-voltage lines that feed houses and apartments. The voltage between any two phases is 380 volts and is called line voltage. And the voltage of the household network is 220 volts. The fact is that in electrical installations with an operating voltage of 380 volts, a neutral wire is provided. If we take one of the phases and the neutral wire, then the potential difference between them will be 220 volts, this is the phase voltage.

Phase detection methods

Before you start electrical work, you should stock up on the necessary devices and tools: an indicator screwdriver or tester, a pointer or digital multimeter, pliers, a marker and a knife for stripping insulation. You also need to find out where the protective equipment is located: circuit breakers or plugs, RCDs. As a rule, they are installed in the switchboard or at the entrance to the apartment. It must be remembered that all operations for connecting electrical equipment and stripping wires can only be carried out with the machines turned off.

The phase can be checked with an indicator screwdriver, this is done as follows. The screwdriver should be clamped between the thumb and middle finger of the hand, without touching the non-insulated part of the sting, then put the index finger on the metal patch from the end of the handle. The bare ends of the wires are touched with a sting, and when touching the phase conductor, the LED lights up. The voltage between conductors can be measured with a multimeter. To do this, the device must be set to the AC measurement limit with the “V” or “ACV” icon and a value greater than 250 V (as a rule, digital devices have a limit of 600, 750 or 1000 V). The probes simultaneously touch two conductors, and this is how the voltage between them is determined. In household electrical networks, it should be 220 V ± 10%.

If the wiring was done in accordance with all the rules, then it is quite possible to determine the phase, zero and ground conductor by the color of the insulation. The insulation of the neutral wire is mainly blue or blue, and the phase wire can be white, black or brown. To make sure that the connection is correct, it is necessary to check the color matching of the insulation not only in the shield, but also in the junction boxes.

First you need to open the shield and inspect the circuit breakers. Their number can be different, it all depends on the design load. Through the machines, only the phase and neutral wires are connected, the grounding conductor is connected immediately to the bus. You should check the color coding of all wires. Further, if the color of the cable insulation that goes into the apartment complies with the rules, you need to open all the junction boxes and inspect the twists. In them, the colors of the insulation should also not be confused. It is worth noting that switches are often connected to the phase in junction boxes. Their installation is carried out with a two-wire wire that has other colors of insulation, mostly white and white-blue. Then it remains only to check the phase wire with an indicator screwdriver.

If your wiring is done without a ground conductor, then you only need to find a phase wire. This is best done with an indicator screwdriver. First of all, turn off the circuit breaker and use a knife to strip the insulation at a distance of 1-1.5 cm. Then you should separate them to a distance that prevents accidental touching of the wires. Then you can turn on the circuit breaker, and touch the stripped ends of the wires in turn with an indicator screwdriver. The glowing diode should point to the phase wire. It must be marked with a marker or colored tape, then turn off the circuit breaker and make the necessary connections. Make sure that the switch is connected to the phase wire, otherwise when changing the light bulbs it will not be enough to turn off the switch, each time you will have to completely de-energize the apartment by turning off the machine.

If your network is three-wire, then in this case you need to determine the purpose of the conductors before installing each element of the network. As in the previous case, identify the phase wire with an indicator screwdriver and mark it with a marker. Ground and neutral wire can be determined using a multimeter. It is worth noting that voltage may appear in the neutral wire due to phase imbalance, basically it does not exceed 30 V. The multimeter should be set to AC voltage measurement mode. With one probe you need to touch the phase wire, and the second in turn to the other two wires. Where the voltage is less, there will be a neutral conductor. If the voltage is the same, then it will be necessary to measure the resistance of the ground wire. To do this, it is desirable to isolate the already defined phase wire in order to avoid accidentally touching it. Using a multimeter, a knowingly grounded element is found, for example, a pipe or a battery. If necessary, they clean the paint and touch one probe of the device to the metal, and the other in turn to the conductors. The resistance of the ground wire with respect to the grounded elements should not be more than 4 ohms, and the resistance of the neutral wire will be even greater.

If all the above measures did not lead to the desired result, then you should contact professional electricians who, using special devices, will call out all circuits. Remember that this is primarily about safety.

estroyka.com

To identify a malfunction of the electric motor at home, in the absence of expensive professional equipment, there is nothing left but to ring the electric motor with a multimeter. With it, you can identify most breakdowns, and you do not have to involve a specialist. So what should be done?

Training

Before diagnosing, you should:

Switch off the unit. If the resistance measurement is carried out in a circuit connected to the mains, the instrument will be damaged.
Calibrate the device, that is, set the pointer to the zero position (the probes must be closed).
Inspect the engine and find out if it is flooded, if there is a smell of burnt insulation or broken parts, etc.

Asynchronous, collector, single-phase and three-phase motors are called by the same method, a small difference in design does not play a special role, but there are nuances that must be taken into account.

Stages of work

The most common malfunctions can be divided into two types:

The presence of contact in a place where it should not be.
Lack of contact in the place where it should be.

First, let's look at how to ring a 3-phase electric motor with a multimeter. It has three coils connected in a delta or star pattern. Its performance is affected by the reliability of contacts, the quality of insulation and proper winding.

First, check for a short to ground (keep in mind that the value will be approximate, as more sensitive instruments are required for accurate readings).
Set the measurement values on the multimeter to the maximum.
Connect the probes to each other to make sure the settings are correct and the device is working.
Connect one of the probes to the motor housing, if there is contact, attach the second probe to the housing and follow the readings.
If there are no failures, alternately touch the probe to the output of each of the three phases.
If the insulation is of good quality, the test should show a sufficiently high resistance (several hundreds or thousands of megohms).

It must be remembered that when measuring insulation resistance with a multimeter, the readings will be higher than permissible, since the EMF of the device does not exceed 9V. The engine runs at 220 or 380v. According to Ohm's law, the resistance value depends on the voltage, so make allowance for the difference.

Then check for shorted turns. When connected by a "triangle", the malfunction indicator will be a larger value at the ends of A1 and A3. When connected with a "star", the device shows an overestimated value in circuit A3.

Knowing that with a multimeter, you will save time and money, since, perhaps, only minor faults will come to light, which you can easily fix yourself. For a more serious and detailed diagnosis, other devices are required, which are rarely used in everyday life due to the high cost. If you cannot find damage with a multimeter, contact a technician.

Checking the collector motor

Now let's move on to the aforementioned nuances, because engines come in different types. How to ring a collector motor with a multimeter? The scheme of its verification is as follows:

Turn on the device by units of ohms and measure the resistance of the collector lamellas in pairs.
Then measure the resistance between the armature body and the collector.
Check the stator windings.
Measure the resistance between the housing and the stator terminals.

Interturn short circuit is determined only by a special device. There is a way to measure armature resistance. Remove the brushes from it and apply voltage to the plates up to 6V, measure the voltage drop between them.

To check a single-phase motor, ring the working and starting windings. The resistance of the first should be one and a half times lower than the second.

For example, let's take a single-phase three-terminal motor used in washing machines (often the old model). If there is very high resistance between the ends, then the coils are connected in series. It remains to find the middle point and thus determine the ends of each of them separately.

Since electric motors are found in every home in household appliances - this is a refrigerator, and a vacuum cleaner, and much more - and they break down periodically, it is simply necessary to know how to check a single-phase electric motor with a multimeter. If the breakdown is not too serious, it is not advisable to carry the device to the repair shop. And you will have the opportunity to gain experience and gain skills by working with engines of various types and modifications.

www.szemo.kz

Inspection and repair of asynchronous electric motors

March 28, 2016, Electrical

How to ring an asynchronous electric motor

How to ring an electric motor with a multimeter

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.

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!

gd-rus.com

How to test and make an induction motor

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 an 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.

Repairing or checking with your own hands an asynchronous electric motor will not be difficult 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 megohmmeter. 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 proceeding with the repair of the 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

A 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 turning off the 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:

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

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

It may burn out as part of the winding and 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 electrical measuring device in the household 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, a motor from an old washing machine has three leads. 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 delta circuit, 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.

It is imperative to ring all the 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, it is not possible to check the insulation resistance value of the motor windings with a multimeter; for this, a 1000-volt megger with a separate power source is required. The device is expensive, but every electrician at work who has to connect or repair electric motors has it.

Be careful not to touch the test clamps while measuring to avoid electric shock.

All measurements are carried out 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, in 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.

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.

Many devices that a person deals with, in their design provide for the presence of an electric motor. During operation, malfunctions may occur in it for various reasons, which will have to be identified and eliminated.

An electric motor is engaged in the conversion of electrical energy into mechanical energy, in order to set in motion various mechanisms and machines. The vast majority of electric motors are rotary motion motors.