Troubleshoot AC 3 phase motors

How to test 3 phase motors

Summary: Learn to troubleshoot 3 phase AC motors.

If you have a 3 phase AC motor that is not functioning properly, then you can use this troubleshooting guide to help you to figure out the problem.

You will first need to unplug the motor from all power sources.

Next you will need to find the 3 input source wires or contacts.

They are most commonly labeled T1, T2, and T3. Shoot each terminal contact to the ground wire. You will normally get an open or infinity Ohms from any terminal to ground, if you get any resistance or zero Ohms, then you have a shorted winding and faulty motor.

Finally, check the terminals to each other. Ohm from T1 to T2 first, next check T2 to T3, and lastly T1 to T3. You should get around 1 to 2 ohms on each test. If you get zero, then the internal windings are shorted together. If you get a very high amount of resistance, or none at all, then the motor windings are open.

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