Development of an on-line monitor to measure motor voltage surges

Voltage surges from switchgear have long been known to lead to stator winding turn insulation failure in large form wound motors. With the widespread introduction of inverter fed drives (IFDs), it now appears that repetitive surges from the IFDs can lead to gradual deterioration and failure. An inexpensive monitor has been developed which continuously measures the risetime, magnitude and repetition rate of surges which strike a motor. In addition to measuring the basic risetime and magnitude data, the monitor also estimates the impact of the total surge history on the life of the insulation. Prototype testing of the system is extremely advanced.