A New Approach to Mitigate CM and DM Voltage dv/dt Value in PWM Inverter Drive Motor Systems

In this paper, a novel passive filter installed at PWM inverter output terminals was proposed with an objective of reducing the high common-mode(CM) and differential-mode (DM) voltage dv/dt value generated by PWM inverter simultaneously. For determining the parameters of the passive filter, the filter transfer function was utilized to achieve a desirable filtering performance. The detailed design procedure of the filter parameters was given. The validity and effectiveness of the proposed filter were supported by the simulation and experimental results carried out on 380V/3kW induction motor system. Further investigations also demonstrate that by making the line-to-line output voltage of inverter sinusoidal, the proposed filter permits motor to be connected with inverter through a long cable. By lowing the dv/dt value of CM and DM voltage, the side-effects induced by them such as shaft voltage, bearing current CM leakage current and over-voltage at motor terminals could be mitigated effectively.