Study On Electric Aging Forinverter-Fed Traction Motorinsulation Based On Nondestructive Parameters

High-speed AC driving locomotive has become the preferred selection for developing railway in China in order to satisfy the need of speed improving. Traction motors are applied in high-speed electric locomotives which enable railway transportation develops toward high speed and heavy loaded. As the key components in AC-drive electric locomotive, the operation performance of traction motor may influence the stability and reliability of the locomotive.PWM inverters with high switching frequency may shorten the rise time of PWM output pulses. They have been widely applied in high-speed AC driving locomotives. The propagation of high frequency PWM waves in power cable lead to over-voltage at the terminals of the inverter-fed traction motor. Meanwhile, equivalent distribution parameters of high frequency circuit of the motor bring uneven voltage distribution between windings. This results in further higher electrical stress on the anterior windings. Thus the failure of insulation windings may restrict the development of high-speed electrification locomotives. At present, the premature failure mechanism of insulation is still unclear. That's the reason why it is necessary and urgent to study on the failuremechanism of the insulation in order to find proper countermeasures.The stator insulation of traction motors are studied by experimental test. According to the structure of motor insulation, two types of sample are designed. One is turn to turn insulation, the other is grounding insulation. The insulation aging properties under high voltage sine waves and high voltage pulse waves are studied. The dielectric loss, capacity, partial discharge parameters under sine wave and pulse wave are tested at different aging period to find out the curve changing direction.