A leakage current of PWM inverter driven induction motor system is discussed. The "Integrated grounding system" is introducing in Japan because of low grounding resistance and low construction price. Though，a leakage current problem of power electronics with this grounding system exists. Leakage current is PWM frequency current，which flow throughCapacitance of insulators to the ground potential greatly increase. The reduction method of leakage current in the integrated grounding system is proposed in this paper. The proposed method is adding a return path of the leakage current to the inverter system. The effect of the proposed method is assured by the experiment. The proposed method can greatly reduce the leakage current from Integrated Grounding Terminal to the earth.

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In the city area，the street is paved with concrete boards. It is impossible to drive the auxiliary electrode in order to measure the earthing resistance. This paper describes the performance of the knitted string mesh earthing electrode as the auxiliary electrode at the street in the city area

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