The impact of adjustable speed drive (ASD) voltage surges on motor stator windings

Experience has shown that high-voltage surges from inverter-fed drives (IFDs), circuit breaker operation and lightning, can cause frequent and severe voltage surges. Such voltage surges can gradually age the turn insulation in motor stator windings. This paper discusses how the surges are created and the impact on motor winding life. Measurements of the voltage surges from different sources are presented. An inexpensive monitor has been developed which continuously monitors and accurately measures the impact of voltage surges on motor stator windings. The monitor measures the risetime, magnitude and repetition rate of the striking surges, and calculates the cumulative impact of the surges on a particular motor. This enables plant personnel to identify those motors experiencing the most severe surge environment and plan for corrective, cost-effective maintenance.