Potential and Temperature Distributions on Stress Grading System of Motor Coil under Repetitive Impulses

Abstract

Recently, it has been pointed out that the erosion of stress grading systems of converter-fed rotating machines may occur by partial discharges and heat generation. It is necessary to measure not only temperature distributions but also potential distributions to grasp the erosion process and to design reliable insulation systems even under inverter surges. Therefore, in this study, the potential distributions under repetitive pulses were measured by a Pockels sensor which covers wide frequency up to GHz. Consequently, it was observed that the field concentrates on the Corona Armor Tape (CAT) closer to the stator core under shorter rising impulse voltage. In addition to this, it has been confirmed that the field concentrates on the CAT during the wave-front of impulses and on Stress Grading Tape (SGT) in the wave-tail of impulses.