Acoustic monitoring of stator winding delaminations during thermal cycling testing

This paper describes a novel technique for acoustic monitoring of insulation delaminations during thermal cycling (TC) testing on a stator bar. Acoustic signals emitted from insulation delaminations within the stator bar were continuously recorded during TC testing. An increase in measured acoustic signals indicates insulation delaminations within the stator bar under testing. In accompanying the acoustic detection, several diagnostic tests, such as dissipation factor tests, partial discharge tests, tap tests, and dissections were performed. These diagnostic test results were compared with the acoustic test results to verify insulation delamination process at various stages. It is concluded that the acoustic monitoring system can indicate which cycle insulation delaminations occurred in and when they occurred in a given thermal cycle during TC testing.