PhD Seminar: An Improvement on Stress Grading System of Medium Voltage Motor Fed by Adjustable Speed Drives

Wednesday, December 12, 2018 10:00 am - 10:00 am EST (GMT -05:00)

Candidate: Alireza Naeini

Title: An Improvement on Stress Grading System of Medium Voltage Motor Fed by Adjustable Speed Drives

Date: December 12, 2018

Time: 10:00 AM

Place: E5 4047

Supervisor(s): Jayaram, Sheshakamal - Cherney, Edward A. (Adjunct)

Abstract:

Nowadays, switches, based on silicon carbide, in the advanced form of adjustable speed drive (ASD), are increasingly used in different industrial processes or domestic appliances. In spite of their benefits, they are introducing new voltage stresses to the stress grading system of form-wound coils of medium voltage (MV) motors. The fast rise time and high repetition rate of the pulsed width modulation (PWM) pulses have adverse effects on the insulation system, particularly the stress grading system of MV motors. Stress grading systems are among the most important part of insulation system of MV motor winding. They are used to prevent partial discharge (PD) in the air gaps between the surface of coils, and also in the end winding region. PD, increasing joule heating, and hot spots are the main reasons for degradation of the main insulation. The present day materials and common tape builds will not be able to reduce the temperature of the hot spots that comes about due to PWM waves.  Therefore, it is essential to find novel configurations or materials to reduce the hot spots under PWM voltages. The proposed research examines the heat produced by PWM voltages in the stress grading system and ways of distributing the production of heat so as to minimize hot spots and uniform the heat production along the stress grading system.