Winding failures in induction machines have been a major concern in the past several years, and more so recently with the addition of variable speed drives (VSDs). Both the introduction of the vacuum breaker, and more recently pulse width modulation (PWM) drives, utilizing fast switching insulated gate bipolar transistors (IGBT's), have brought an increase in winding failures in induction machines. Recently the Office of Naval Research (ONR) has developed a 15 phase IGBT motor drive in conjunction with an ALSTOM 25,500 hp induction machine for use in ship propulsion. In preliminary testing the machine windings have displayed the onset of corona, which is the beginning of winding damage. One cause of corona is motor overvoltages.; There are at least two mechanisms causing winding failures: steep-fronted surges, like those caused during the opening and closing of vacuum breakers, and transient overvoltages caused by impedance mismatch between cable and load during VSD operation. There has been a fair amount of work done to date on the propagation of vacuum breaker-induced, steep-fronted surges in the windings of the induction machine. More recently, work has been progressing on overvoltages at the machine terminals as a result of VSD's operating with long cables connecting drive and machine.; This dissertation presents an overview of the work done in both areas and the need to bring the two areas of work together, to achieve a more complete understanding of the effects of VSDs on induction motor windings. While the majority of previous work has focused on modeling, the accurate measurement of parameters on actual machines for investigation of this problem has not been addressed in detail. That is the main focus of this dissertation.
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