Aging Model Of Polyimide Film Under Paulse Voltage

The higher safety and reliability of the traction power system are absolutely required for the rapid development of High-speed Railway and Heavy-duty Rail Transport. The polyimide film is the main material of the traction motors' insulation, which bears the pulse voltage with high volt and rapid rising edge and large repetition rate. In this paper, the chief topic is talking about the relationship between the aging life of polyimide film and voltage level, frequency and temperature.First, it's necessary to develop a instrument to record the aging life of the test samples. According to experience, it's hard to extract the break-down signals of the test samples under high pulse voltage by current sensors and voltage dividers. So, this paper presents a new device which base on thermal sensors and micro-computer. It can calculate the change rate of the signal by difference algorithm exactly. When the change rate and amplitude of the signal exceed the limit, the signal can be considered as the break-down signal of the test samples.Second, the aging experiments of the polyimide film under different voltage level, frequency and temperature have been executed and find out the aging law of the film in this paper. The aging life of the film decay linearly following the growing of voltage between 800volts and 1500volts. The aging life of the film decay in index movement following the growing of temperature between 80℃and 150℃However, the curve of the aging life is mostly smooth when the temperature rises over 110℃and this indicates that the polyimide film owns a wonder heat tolerance. The aging life of the film decay in inverse power law following the growing of frequency between 1 kHz and 10 kHz.Last, the relationship of the aging life and partial discharge has been discussed. The main reason of the insulation failure of the traction motors is partial discharge occurred in the inner and on the surface of insulation material. The voltage level, frequency and temperature can easily change the parameters of the partial discharge, so, of course, they can affect the aging life.