why we are testing cables with DC supply not with AC supply?
Answer Posted / udhaya shankar
DC alone is used because we need to measure only the resistance of the winding (or) cable insulation. If we use AC to conduct the insulation test, we will be measuring impedance instead of the resistance as the insulation has a substantial capacitive reactance.
The health of the winding (or) cable is best indicated by its resistance and not its impedance. This is why only DC is used to measure the insulation resistance
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