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Method of detecting motor with megohmmeter

time:2021/1/7   source:华天电力  reading:237 time

Step 1: Use a megger to measure the motor's ground insulation

Note that for a 380V motor, a 500V megohmmeter should be used. For example, a 1000V or 2500V megohmmeter may break the motor insulation.

Place the megohmmeter flat, shake the rocker of the megohmmeter at a speed of 120 revolutions per minute, and measure the insulation between the motor terminal and the motor housing, not less than 0.5 megohm, of course, the higher the insulation value, the better, in actual work Generally tens of megabytes, hundreds of megabytes or even infinite, if the insulation to the ground is too low, the motor should be considered for maintenance.

Insulation Resistance Tester.png

For a wound motor, the insulation between the tester and the rotor, and between the rotor and the ground is qualified.

Step 2: Use a megger to measure whether the three-phase resistance is balanced

If the motor connection piece is not removed, the motor can be connected in a star shape, and the resistance value between each phase and the star point can be measured. The resistance value of the three phases should be basically equal, and the motor can be connected to the angle shape, and the resistance value should be basically equal. If the measured three-phase resistance of the motor is severely unbalanced, there may be a short circuit between turns.

The third step: also check the mechanical parts of the motor

For example, whether the bearing is good or bad, whether the motor is bored, you can manually turn the motor when the motor is under no load to observe whether the motor rotates lightly and whether there is abnormal noise.

If there is no abnormality in the above inspections, you can power on the motor for an experiment. After power on, observe whether the motor runs smoothly without vibration and whether the current is normal.

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