Electric Motor Megger Test

For a three phase motor insulation resistance is usually measured between each motor winding or phase and between each motor phase and motor frame earth using an insulation tester or megger.

Electric motor megger test.

Insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail. How to test a three phase electric motor has been discussed in this article. Baker instruments is a leading provider of test equipment for the electrical condition monitoring of motors generators and coils. Check c to e s to e r to e.

The insulation resistance tester generally known by its trade name megger is capable of providing critical information regarding the condition of motor insulation. Insulation resistance quality of an electrical system degrades with time environment condition i e. Minimum test value for a good electric motor is at least 1mω running amps test with the motor running check the full load amps fla with a suitable meter or preferably a clamp on meter and compare with the motor name plate fla. If you want to test a 480v motor then the voltage required would be 1000v with a reading of 2m ohms or more.

You can test your motor insulation with the help of a megger. Temperature humidity moisture and dust particles. When it comes to checking out electric motors there are special measuring instruments that may be used to detect and diagnose malfunctions. Step 3 crank the handle for about a minute and notice the resistance reading.

Place one megger probe to the any mounting bolt on the breaker box to test for grounding continuity then touch the other probe to a motor terminal. Reverse side of card at right is used to record the test data. Deviations from rated fla could signify problems with the motor under test. Figure 4 typical record of insulation resistance of a mill motor.

Curve a shows test values as measured. Whether you are testing in a motor repair shop in an industrial plant on a ship or up a wind turbine baker instruments motor test equipment allows you to fully understand the condition of the motor the power supply and the load. The megger test is a method of testing making use of an insulation tester resistance meter that will help to verify the condition of electrical insulation. Curve b shows same values corrected to 20 c see page 22 giving a definite downward trend toward an unsafe condition.