Method of judging the quality of motor by multimeter
There are three-phase motors and single-phase motors, and single-phase motors have three lines and six lines.
three-phase motor
Six taps for three-phase winding of phase motor. Let's first remove the connecting piece connecting the motor terminal. Measure the beginning and end of each phase winding with a multimeter to see if it is on or off. Then use a multimeter to measure the resistance between each two-phase winding, at least greater than 0.5 megohm, and the greater the better. Finally, measure the insulation resistance between each phase winding and the motor shell, which should also be infinite. In this way, the quality of three-phase motor can be judged basically.
Single-phase motor with three wires
A unidirectional motor has only two windings, a starting winding and a running winding. One of the three wires is their common wire, that is, one end of the two-phase winding is connected together. The other two are the other taps of the two-phase winding.
The resistance between the two taps should be maximum and equal to the sum of the resistance values of the two windings.
Of course, we have to measure the resistance between the coil and the casing to see if it has been broken down. Of course, the greater the resistance, the better, and the lowest is the same, not less than 0.5 megohm.
6-wire single-phase motor
There are six lines, in fact, two lines (Z1, Z2) are centrifugal switch lines. This kind of motor also has six terminals, so its connecting piece should be removed. Remove the capacitor, and then measure the end of the two-phase winding and the resistance between the two-phase windings respectively. The method is the same as that of three-phase motor.
Using multimeter to judge the quality of motor can only be a preliminary judgment. The insulation resistance between windings and the insulation resistance of each phase winding to the ground should be measured by megger to be more accurate.
Also, the short circuit between turns of winding can't be measured. We can only guess whether there is a short circuit between turns by comparison. For example, the winding structure of one phase is much smaller than that of the other two phases, so we can suspect that it has turn-to-turn short circuit.
