Motor Insulation Resistance Test Procedure Pdf

At c the insulation resistance value after the motor has been rewound.

Motor insulation resistance test procedure pdf.

The measurement of insulation resistance is carried out by means of a megohmmeter high resistance range ohmmeter this is how the test works. During the measurement and immediately afterwards some of the terminals carry dangerous voltages and must not be touched. The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. The test should also be performed after a motor is.

Motor so the insulation resistance has returned to a higher value and has remained stable over time indicating a good conition. Smaller systems will remain steady because the capacitive and absorption currents drop to zero faster than on larger systems. 1000 100 10 1 12 3 4 56 7 89 10 time in minutes reading in megohms d e figure 2 absorption curve of test conducted on 350 hp motor. Loss of insulation resistance of an electric motor is one of the first signs of motor failure.

When performing insulation resistance testing you must maintain consistency. Dc voltage of 500 or 1000 v is applied between the windings and the ground of the motor. Larger insulation systems will show a steady decrease. Regular checks of motor insulation resistance the key to prolonging the life of any electrical device is periodic checks maintenance the insulation resistance of stored and active motors should be checked regularly.

It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. For a three phase motor the isolation resistance can usually be measured between each motor winding or phase and between each motor stage and motor frame earth by an insulation tester or megger 4. Insulation resistance test insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail. An insulation spot test is an insulation resistance test that can be used to verify the condition of the insulation over the life of the motor.

Curve indicates a e potential problem. The test measures the insu lation resistance between the phases and or between phase and ground. Insulation resistance testing is a non destructive test procedure. Aemc instruments testing methods based on the influence of the test voltage application time pi dar these methods involve measuring successive insulation resistance values at specified times.

After 1 min you should read and record the resistance value. Curve d indicates a good insulation with an excellent polarization index of 5. A spot test should be performed at reg ular intervals every six months for ex ample to track the changes in insulation integrity. With a little record keeping and common sense however you can get a good picture of the insulation condition from values that are only relative.

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. Insulation resistance decreases in temperature or moisture. Insulation resistance testing purpose.