Measurement method for simply judging three-phase asynchronous motor faults using a multimeter
1: Inter-turn short circuit. Adjust the multimeter to the ohm range, measure each winding, and check whether the three-phase windings are equal in resistance (actually there is a deviation, but the deviation is very small). For star-connected motors, measure the first end of the winding and the common end. For delta-connected motors, measure both ends of each winding. If the resistance of one of the three-phase windings is much smaller than that of other windings, it can be determined as an inter-turn short circuit. If there is only a deviation, but the deviation is not large, but there is doubt, it is recommended to use a bridge to measure. The measurement accuracy of the bridge is much higher than that of the multimeter, and the multimeter can only make a rough judgment on the inter-turn short circuit. PS: The three-phase resistance value deviation of the motor winding is ≤±5%, and the motor must be kept in a static state during measurement.
2: The winding is short-circuited to the ground and the winding hits the shell. Measure the insulation resistance between the winding and the shell or the ground. If it is zero or the resistance is very small, it can be judged that the winding is short-circuited to the ground and the winding hits the shell. If it is larger than 1M, it is normal. PS: The multimeter can only make a rough judgment. It is recommended to use a megger for retesting.
3: Inter-turn circuit break, winding burned out. Measure the resistance of each winding. If it is infinite or very large (much larger than the resistance of a normal winding), then it should be a circuit break between turns or the winding is burned out. PS: Turn-to-turn circuit breakage and winding burnout can only be determined by disassembling the motor.
Multimeter ground continuity test method
With a multimeter, you can measure the resistance between two wires through the resistance setting. Use the resistance value to determine whether the two wires are connected properly. For example, if it is short-circuited, the resistance value is zero, and if it is open circuit, the resistance value is infinite. If there is A certain contact will have a certain resistance. Grounding is to measure the resistance between the wire you want to know and the ground wire.
You can judge by measuring the resistance between each section of the ground wire and the main ground wire. Generally, the ground resistance is required to be less than 4 ohms. The accuracy of the multimeter may not be too high. You can only make a rough judgment. If you want to be more precise, you can find a special Use a ground meter or some electrical bridge to measure.
