Inverter drive issues and magnet wire responses

Abstract

Inverter driven motors save energy and provide versatility to manufacturing and other processes. Drives allow relatively lower cost motors to run at variable speeds, but the higher voltage spikes generated by some drives have been linked to premature failure of otherwise reliable motors. Failure analyses of some of these motors have shown evidence of partial discharge damage. Motor manufacturers have scrutinized their manufacturing processes and materials to develop motors that are much more resistant to this type of failure mechanism. Magnet wire companies have developed products that are much more resistant to partial discharges, but some motors are still failing due to the continual bombardment of high voltage spikes generated by the switching devices in the drives. Much more data has been generated on corona inception and extinguish voltages in an effort to better understand the problem. This paper attempts to qualify and quantify some of the issues related to premature failure of motors running on IGBT drives. Benefits of using some different types of magnet wire insulation are explained. Specific data related to CIV vs. magnet wire insulation build are presented.