How to Calculate Minimum Insulation Resistance of Motors
The minimum insulation resistance of any motor, Rmin, can be calculated by multiplying the rated voltage, VR, with the constant factor 0.5 MΩ /kV:
Rmin = 0.5*VR
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:
(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 need to be dried.
(b) For a motor in operation, the minimum insulation resistance may drop to a critical level. If the measured value of insulation resistance is greater than the calculated value of minimum insulation resistance, the motor can continue to run. However, if it drops below this limit, the motor has to be stopped immediately to prevent harm to personnel due to the high leakage voltage
The minimum insulation resistance of any motor, Rmin, can be calculated by multiplying the rated voltage, VR, with the constant factor 0.5 MΩ /kV:
Rmin = 0.5*VR
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:
(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 need to be dried.
(b) For a motor in operation, the minimum insulation resistance may drop to a critical level. If the measured value of insulation resistance is greater than the calculated value of minimum insulation resistance, the motor can continue to run. However, if it drops below this limit, the motor has to be stopped immediately to prevent harm to personnel due to the high leakage voltage
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