Electric Motor Megger Test

Insulation resistance quality of an electrical system degrades with time environment condition i e.

Electric motor megger test.

You can test your motor insulation with the help of a megger. Deviations from rated fla could signify problems with the motor under test. The ideal mode of testing is phase to phase and phase to ground. 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.

Megger makes electrical test equipment to help you install improve efficiency and extend the life of electrical assets and cable networks at high medium and low voltage. The insulation resistance tester generally known by its trade name megger is capable of providing critical information regarding the condition of motor insulation. Check c to e s to e r to e. Figure 3 typical scale on the megger insulation tester.

Figure 4 typical record of insulation resistance of a mill motor. 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. Temperature humidity moisture and dust particles. Insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail.

Step 3 crank the handle for about a minute and notice the resistance reading. Reverse side of card at right is used to record the test data. When it comes to checking out electric motors there are special measuring instruments that may be used to detect and diagnose malfunctions. Curve a shows test values as measured.

If you want to test a 480v motor then the voltage required would be 1000v with a reading of 2m ohms or more. Curve b shows same values corrected to 20 c see page 22 giving a definite downward trend toward an unsafe condition. 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. 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.