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.
Motor insulation resistance test procedure pdf.
Insulation resistance testing is a non destructive test procedure.
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.
Dc voltage of 500 or 1000 v is applied between the windings and the ground of the motor.
Smaller systems will remain steady because the capacitive and absorption currents drop to zero faster than on larger systems.
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.
Ground insulation test of a motor.
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.
The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms.
Loss of insulation resistance of an electric motor is one of the first signs of motor failure.
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.
During the measurement and immediately afterwards some of the terminals carry dangerous voltages and must not be touched.
After 1 min you should read and record the resistance value.
Motor so the insulation resistance has returned to a higher value and has remained stable over time indicating a good conition.
Insulation resistance decreases in temperature or moisture.
A spot test should be performed at reg ular intervals every six months for ex ample to track the changes in insulation integrity.
At c the insulation resistance value after the motor has been rewound.
Insulation resistance testing purpose.
Insulation resistance test insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail.
Larger insulation systems will show a steady decrease.
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.
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.
Curve d indicates a good insulation with an excellent polarization index of 5.
The test measures the insu lation resistance between the phases and or between phase and ground.
When performing insulation resistance testing you must maintain consistency.
The test should also be performed after a motor is.
A if the insulation resistance of a new cleaned or repaired motor that has been stored for some time is less then 10 mω the reason might be that the windings are humid and.
Set the voltage.
