Insulation Ageing Testing System Based On Continous High Voltage Square Wave Pulse

With the development of high-speed railway, the AC driving locomotive requires more advanced performance. The variable-frequency pulling motor, as the key component of the locomotive, has great relations with the stability and reliability of the system. The typical output signal of the variable-frequency driving system is the square-wave with steep rising edge. When the signal acts on the pulling motor, the insulation of the winding will be aged more quickly. In order to assure the reliability and safety, it's imperative to develop the diagnostic technology for the winding insulation and the evaluation methods of the residual lifetime.In order to study the relationship between the square-wave and the winding insulation of the pulling motor, a testing system of insulation aging was developed, which can analog the real condition of the pulling motor. According to the voltage waveform and the rule of the accelerated aging test, a testing power was designed composed with high frequency pulse generator and high frequency pulse transformer. The DC power is got by using the new switching device and the three phase non-controlled rectification circuit. Then the DC power passes the chopper circuit and the full-bridge inversion circuit. The continuous variable-frequency square-wave is generated at last. To assure the reliability of the high-frequency pulse power, the over-voltage protection and the triple over-current technology is also exploited. After analyzing the output signal character of the high frequency pulse transformer, a new design scheme was adopted. The primary side of the high frequency pulse transformer is installed in parallel and the secondary connection in series. This method can generate high frequency pulse with high rate of voltage rise, wide output frequency band and small waveform distortion.In order to verify the reliability of the system, the test on lifetime curve of the polyimide, which is the material of pulling motor used for the grounding insulation, was realized. In addition, the lifetime models with vary amplitude of pulse, frequency and ambient temperature were obtained. The results proved the high reliability and practicability of the system. It satisfied the need of the aging test of pulling motor insulation. The parameters have reached the international norm of the homogeneous testing system. The life models create conditions for studying the failure mechanism of the insulation of the variable-frequency pulling motor winding.