How to use a multimeter to measure the quality of a motor
Three-phase motor measurement method:
Put the digital multimeter on the 200Ω gear, and measure the three-phase power lines on the motor two by two. If the resistance values measured three times are equal or very close, it means that the three-phase windings are well connected.
Then open the junction box of the motor, remove the connecting copper piece on the terminal, that is, disconnect the three windings U, V, W, put the multimeter gear on the maximum gear of the resistance gear, or use the multimeter test pen. Measure any end of the U, V and W windings two by two. If the resistance values show infinity, it means that the motor phase-to-phase insulation is normal.
Finally, use the maximum resistance gear of the multimeter to measure the resistance value of any end of U, V, W and the casing. If the resistance value is infinite, it means that the motor insulation is no problem, and it can be powered on and tested to start.
Measurement method of single-phase motor:
When measuring a single-phase motor, you can put the gear of the digital multimeter to 2K, and first measure the resistance of the main winding, which is generally in the range of tens to hundreds of Ω, which varies according to the power of the motor.
The resistance of the secondary winding is slightly larger or the same as that of the main winding. If the resistance of the primary and secondary windings is normal, then measure the insulation between the primary and secondary windings, and put the multimeter gear on the maximum resistance gear. When the primary and secondary windings are disconnected, connect a test lead to the main It is normal for the insulation resistance to be infinite on any terminal of the winding and the other end of the grounding secondary winding. Finally, the insulation resistance of the two windings and the casing is also measured. One test lead is connected to the winding, and the other is connected to the motor casing. Where it can be turned on, it is normal to display infinity.
