Often the question arises, 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: an external inspection, a special stand, a “ringing” windings with a multimeter. The latter method is the most economical and universal, but it does not always give the right results. For most of the constants, the resistance of the winding is almost zero. Therefore, an additional circuit for measurements is required.
Motor design
To quickly learn how to check the electric motor, you need to clearly imagine the arrangement of the main parts. All motors are based on two parts of the structure: the rotor and the stator. The first component always rotates under the influence of an electromagnetic field, the second is stationary and just creates this vortex flow.
To understand how to check the electric motor, you need to disassemble it with your own hands at least once. Different manufacturers have a different design, but the principle of diagnosing the electrical part remains unchanged. Between the rotor and the stator there is a gap in which small metal chips can accumulate during depressurization of the housing.
When worn, the bearings may give an overestimated current, so the protection will knock out. When dealing with the question of how to check the electric motor, one should not forget about mechanical damage to the moving parts and the boron where the contacts are located.
Diagnostic difficulties
Before checking the electric motor with a multimeter, an external inspection of the case cooling the impellers should be carried out, and the temperature should be checked with the touch of a hand on metal surfaces. A heated case indicates an excessive current due to problems with the mechanical part.
It will be necessary to analyze the condition of the insides thoroughly, check the tightness of bolts or nuts. With unreliable connection of live parts, failure of the windings can occur at any time. The surface of the engine must be cleaned of dirt and no 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 a multimeter, you will need clamps for non-contact measurement of the current passing through the wire.
- A multimeter can measure only slightly high resistance. A megohmmeter is used to check the insulation state (where the resistance is from kΩ to MΩ).
- To draw conclusions about the suitability of the motor, you will need to disconnect the mechanical components (gearbox, pump and others) or you need to be sure that these components are fully functional.
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 motor winding, you need to disconnect 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 down, you can measure the incoming voltage in order to be sure that the electronic circuit is working.
In engines of household appliances, a design with a starting winding is often used, the resistance of which exceeds the value of the working inductance. When measuring, take into account the fact that collector brushes may be present. In the place of contact with the rotor, soot often appears, having cleaned it, it is necessary to restore the reliability of the fit of the brushes during rotation.
Small-sized engines with one working winding are used in washing machines. The whole essence of diagnosis is reduced to measuring its resistance. Current is measured less often, but by taking characteristics at different speeds, conclusions can be drawn about the health of the motor.
Details of the diagnosis of the electrical part
Consider how to check the health of the electric motor. First of all, contact connections are examined. If there is no visible damage, then open the junction of the wires with the engine and turn them off. It is advisable to determine the type of motor. If it is 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 should be the same in all cases. If there are short-circuited sections or their breakage, then the motor tachometer must be replaced. If you “ring” the rotor coil itself, then a 12 V multimeter may not be enough. To accurately assess the condition of the winding, an external power source is required. It can be a PC unit or a battery.
To measure small resistance values , a resistor of known nominal value is installed in series with the measured winding. It is enough to choose a resistance of about 20 ohms. After applying power 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 more often performed in the form of typesetting plates with a magnetic core. Phase windings are often motionless and located in the stator.
With a multimeter, it is much easier to check such a motor. An ohmmeter needs to ring the resistance of each winding. It should be the same. Do not forget to check the breakdown on the case by measuring the resistance on the case. However, it is more reliable to check the insulation with a megohmmeter.
Answering the question of how to check the motor windings with a tester, it should be noted that “phase imbalance” in an induction motor is not allowed. The resistance difference should not exceed one ohm. Otherwise, the current at a lower inductance increases, which leads to the burning of the winding.
If a DC motor
For such motors, the winding resistance is very small and measurements are made using two instruments. At the same time, readings are taken from the ammeter and voltmeter. A battery voltage of 4-6 V is selected as the source. The resulting value is determined by the formula R = U / I.
Check all the available resistance of the armature windings, measure the values ​​between the collector plates. All indicators of the multimeter should be equal. From this comparison, we can draw conclusions on 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 construct, the motor will be normal when the difference in values ​​is 30%. The readings of the multimeter do not always give an accurate prediction of the state of the washing machine's engine. Additionally, often an analysis of the motor on a calibration bench is 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. The type of construction of the electrical part depends on this. With a multimeter, they ring the windings and draw conclusions about their integrity.
The performance check is carried out after replacing the Hall sensor. It is he who fails in most cases. After windings are ringed, 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 flip the plug in the socket by turning it with other contacts.
This simple method helps 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
First of all, it is recommended to immediately pay attention to the condition of the brushes, wiring. Nagar on live parts indicates abnormal engine operation. The current collectors themselves should be smooth, without chips and cracks. Scratches also cause sparking, which is detrimental to motor windings.
In washing machines, the rotor often warps, because of this, the lamellas are chipped or broken. The control board constantly monitors the position of the rotor through the Hall sensor or tachogenerator, adding or decreasing the voltage applied to the working winding. From here there is a strong noise during rotation, arcing, violation of the operating modes during the spin cycle.
This phenomenon can be seen only during the spin cycle, and the washing mode is stable. Diagnosis of the operation of the machine does not always go through an analysis of the state of the electrical part. Mechanics can cause malfunctions. Without load, the engine can spin quite evenly and stably gain speed.
If nevertheless knocks out protection?
After taking measurements with floating faults, it is not recommended to connect to the network for verification. You can permanently disable the motor without suspecting the problem. How to check the motor winding with a multimeter, the service center master will tell you by phone. Under his leadership, it will be easier to determine the type of design and the procedure for diagnosing a faulty washing machine.
However, often and experienced craftsmen can not cope with the repair of complex cases when the malfunction is floating. For verification in the service it is required to use a washing machine, mechanical components are crucial. Skewing the motor shaft is a special case of problems with the rotation of the drum.