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

Often the question arises as to how to check the electric motor after failure, as well as after repair, if it does not rotate. To do this, there are several ways: external inspection, a special stand, "winding" of windings with a multimeter. The latter method is the most economical and universal, but it does not always give correct results. For most of the constants, the resistance of the winding is practically zero. Therefore, an additional scheme for measurements is required.

Motor construction

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

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

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

Difficulties in diagnosing

Before checking the motor with a multimeter, an external inspection of the cooling fan housing should be carried out, and the temperature should be checked by touching the metal surfaces with a touch of the hand. Heated housing indicates an overestimate current due to problems with the mechanical part.

Analyze the state of the boron interiors, check the tightening of bolts or nuts. With an unreliable connection of live parts, the failure of the windings can occur at any time. The surface of the engine must be cleaned of dirt, and there should be no moisture inside.

If we consider the question of how to test the electric motor with a multimeter, then it is necessary to take into account several nuances:

• In addition to the multimeter, pliers are needed for contactless measurement of the current passing through the wire.
• A multimeter can measure only slightly high resistance. To check the insulation state (where the resistance is from kOhm to MOhm), use a megohmmeter.
• To draw conclusions about the suitability of the motor, you need to disconnect the mechanical components (reducer, pump and others) or you need to be sure of the full serviceability of these components.

Switching equipment

To start the rotation of the windings, a board or relay is used. To begin to understand the question of how to check the winding of the motor, it is necessary to disconnect the supply chain. Through it, the control board elements can "ring", which will make an error in the measurements. With the wires thrown off, the incoming voltage can be measured to be sure that the electronic circuitry is working.

In engines of household appliances, a design with a starting winding whose resistance exceeds the value of the working inductance is often used. When measuring, take into account the fact that there may be current collectors brushes. In the place of contact with the rotor, there is often a deposit, cleaning it, it is necessary to restore the reliability of the fitting of the brushes during rotation.

In washing machines small-sized motors with one working winding are used. The whole point of the diagnosis is reduced to measuring its resistance. The current is measured less often, but to remove the characteristics at different speeds, you can draw conclusions about the serviceability of the motor.

Electrical fault finding details

Let's consider how to check the serviceability of the electric motor. First of all, inspect the contact junctions. If there is no visible damage, then open the place of connecting the wires to 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 in the place where the brushes fit.

It is required to measure the ohmmeter resistance between each adjacent lamellae. It should be the same in all cases. If there are short-circuited sections or their breakage, then the motor tacho sensor needs to be replaced. If, however, "ringing" the rotor coil itself, then a 12 V multimeter may not be enough. To accurately assess the state of the winding, you need an external power source. It can be a block from a PC or a battery.

To measure small values of resistance in series with the measured winding, a resistor of known denomination is installed. 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 the resistor is measured. The resulting value is obtained from the formula R1 = U1 * R2 / U2, where R2 is a resistor, and U2 is the voltage drop across it.

Diagnostics of asynchronous motors

On industrial washing machines , powerful three-phase electric motors can be used. The rotor is more often performed in the form of dial plates with a magnetic core. Phase windings are often stationary and located in the stator. With a multimeter, this motor is much easier to check. The ohmmeter needs to ring the resistance of each winding. It should be the same. Do not forget to check the breakdown on the body by measuring resistance on the case. However, it is more reliable to check the insulation with a megaohmmeter.

Answering the question how to check the windings of the electric motor by the tester, it should be noted that the "phase skewing" of an asynchronous motor is not allowed. The difference in resistance should not exceed one ohm. Otherwise, the current of the smaller inductance increases, which leads to burn-in of the winding.

If the DC motor

For such motors, the resistance of the winding is very small and measurements are made using two instruments. At the same time, readings are taken from the ammeter and the voltmeter. The source is a battery with a voltage of 4-6 V. The resulting value is determined by the formula R = U / I.

Check all available resistance of the armature windings, measure the values between the collector plates. All the parameters of the multimeter must be equal. On this comparison, you can draw conclusions about how to check the motor armature.

The difference in resistance readings between adjacent collector plates is allowed no more than 10%. When an equalizing winding is provided in the construction, the motor will operate normally with a difference of 30%. The meter reading does not always give an accurate prediction about the state of the engine of the washing machine. In addition, it is often necessary to analyze the operation of the motor on a calibration bench.

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 determines the type of design of the electrical part. With a multimeter, windings are called and conclusions are drawn about their integrity.

The performance is checked after the Hall sensor has been replaced. It is he who breaks down in most cases. After winding the windings with their integrity, experienced masters recommend connecting the motor directly to the 220 V network. As a result, a uniform rotation is observed to change its direction, it is possible to poke the plug in the socket by turning it with other contacts.

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

Diagnostic sequence

The first step is to immediately pay attention to the status of brushes, wiring. The carbon on live parts indicates abnormal operation of the engine. The current collectors themselves should be smooth, without chips and cracks. Scratches also lead to sparking, which is detrimental to engine windings.

In washing machines, the rotor is often skewed, because of this, chips or breakage of lamellas occur. The control board constantly monitors the position of the rotor through the Hall sensor or tachometer, adding or reducing the voltage applied to the working winding. Hence, there is a strong noise during rotation, sparking, violation of operating modes during spinning.

This phenomenon can be seen only when spinning, and the washing schedule is stable. Diagnosis of the machine does not always go through the analysis of the state of the electrical part. Mechanics can be the cause of malfunction. Without load, the engine can rotate quite evenly and steadily gain momentum.

If you still beat the defense?

After the performed measurements for floating faults, it is not recommended to connect to the network for verification. It is possible to disable the motor completely, without suspecting the problem. How to check the winding of the motor with a multimeter, the master of the service center will tell 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 and experienced masters do not cope with repairing complex cases when the malfunction is floating. For checking in the service it is required to use a washing machine, mechanical nodes are crucial. The misalignment of the motor shaft is a particular case of problems with the rotation of the drum.