Step 4: Test the insulation resistance of the motor and note down the readings of insulation resistance. Better to go with the IEEE’s recommendations. Remember that if the selected test voltage is too high, the applied test voltage may even damage the insulation. Refer to the below image.įollow the below table for selecting suitable DC voltage as per IEEE 43-2013 standard. Plug one end of the red lead to the Voltage / insulation terminal and another to the winding U1. You can connect the black lead there also. Standard motor manufacturers provide a separate terminal for grounding inside the motor terminal box. You may get an erroneous reading if you do not remove the paint. The layer of paint acts as an insulation. Remove the paint applied to mounting bolts. The mounting bolts are the best place to connect. Plug one end of the black lead of the insulation tester to the common terminal of the meter and other end to the body of the motor or a good ground terminal. Step 2: Connect the insulation resistance tester to the motor.
So, always remove the power cable connected to the motor.Ĭhecking Insulation resistance between ground and each winding of the motor Performing insulation testing can damage electronics like motor drives, PLCs, transmitters, sensors, etc. The insulation tester uses higher DC voltage. Also, the leads that are connected in star or delta. Step 1: Disconnect the power cables of the motor.
MOTOR WINDING RESISTANCE HOW TO
How to check insulation resistance of motor? Checking Insulation resistance between each winding of the motor.Checking Insulation resistance between ground and each winding of the motor.How to check insulation resistance of motor?.So, leave the leads connected when you stop the test.ĭo not use the tester in an explosive atmosphere. The insulation tester can discharge any residual test voltage. You must have an insulation resistance tester to check the insulation. In this article, I would give you step-by-step guidance on – how to check insulation resistance of motor with illustrations. The point ‘D’ indicates the condition of insulation of the motor after rewinding.Īnother situation is, let’s say you have a new motor, kept idle for a long time – say more than 2 months, then you must check its insulation resistance before you put the motor for operation. Either you have to replace it with a new one or rewind the old motor. In this case, you can no longer continue to use the motor. The point ‘C’ indicates the motor insulation failure. the motor insulation resistance decreases as indicated by point ‘B’. You can see the motor insulation deterioration.Īt point ‘A’ the motor is put on service.ĭue to aging, contamination, temperature, moisture, etc.
Motors running continuously require insulation checks periodically.