IGBT在NaCl环境下硅凝胶绝缘表面放电的拐点现象及形成机理

As the core component of offshore wind power converter, the encapsulated silicone gel insulation material of insulated gate bipolar transistor (IGBT) module is prone to deterioration under the long-term action of ocean salt fog operation environment. In order to study the surface discharge of silicone gel in salt fog environment, this article designs a discharge experimental platform and measurement samples. Based on the partial discharge measurement results along the sample surface under square wave voltages, it is found that the number and phase of surface discharge of silicone gel under the salt fog environment are positively correlated with the voltage frequency. Meanwhile, the amplitude and the phase of discharge under the ocean standard condition show an increase of 54.4% and 32.8% compared with those under the condition without salt fog. Furthermore, the measurement finds that there is a special frequency-induced inflection point phenomenon of surface breakdown voltage at 15 kHz under the salt fog environment. Therefore, a mathematical model of the inflection point is established by further combining the influencing mechanism of salt fog ions and voltage frequency on the discharge, and the calculated inflection frequency of 16.99 kHz is close to the measurement result. The results of this article can provide theoretical support for the characteristics and mechanism of surface discharge of IGBT silicone gel insulation under salt fog environment.