Study on breakdown of magnet wire used in AC traction motor

AC traction motors are fed by fast switching inverters in express locomotive. Inter-turn insulation of AC traction motors is electrically more stressed than that in the conventional. In order to investigate the service life of AC traction motors, mechanism and characteristics of dielectric breakdown of magnet wire used in AC traction motors are studied in the paper. Experiments have been carried out on specimen according to the condition of AC traction motor. Aging factors of magnet wires under continuous pulses are introduced and influence of inorganic fillers on insulation aging is analyzed. Breakdown points are analyzed through energy spectrum analysis and electron microscopic photograph. Finally, the breakdown mechanism of magnet wire is explained by conducting micro-crack theory.