Effectiveness of stress control coatings in medium voltage form wound coil ends under fast rise time pulses and contamination

Abstract

The paper discusses the effectiveness of stress control coatings on the ends of 4 kV motor coils under fast rise time pulses that arise from PWM drives. The analysis of the stress relief is done using a transient finite element method and the results are compared to experimental measurements. Currently adopted stress control coatings do not effectively grade the electric stress arising from fast rise time pulses from PWM inverter drives which easily reaches the partial discharge threshold on the ground wall insulation surface of the form wound coils. Electric field enhancement is shown to be considerably greater under polluted conditions. In this work, changes to the properties of the coatings are suggested as a solution to improve the effectiveness of stress control coatings on form wound coils in motors connected to inverter fed drives