Common-mode currents in drive systems using PWM inverters: Project of a filter topology for their mitigation

Abstract

This paper provides a characterization of high-frequency leakage currents in PWM inverters feeding AC motors, contextualized in the analysis of an actual case in which the motor presents premature and recurring failure of its bearings, due to circulation of electric current. From the parameters of an equivalent circuit, in terms of cables, motor and inverter return path, a filter is proposed for mitigation of common-mode currents and related phenomena, characterized by a common-mode transformer. Results from simulations and experimental results show that the proposed transformer represents an advantageous alternative in respect to traditional RC and RLC filters, since, in addition to mitigating common-mode phenomena, the transformer dissipates a negligible amount of power.