A reduced switch dual-bridge inverter topology for the mitigation of bearing currents, EMI and DC-link voltage variations

This paper presents a reduced switch count dual-bridge inverter approach for the mitigation of motor bearing currents and EMI, at a lower drive cost. The proposed inverter employs two four-switch inverters and is controlled to generate balanced excitation of dual voltage rating induction motors under PWM operation. The proposed approach eliminates the common-mode voltage and thus prevents the motors from premature bearing failures in addition to reducing the conducted EMI. Compared to the conventional four-switch inverters, the proposed inverter also eliminates the single-phase circulating current and voltage variations across the DC-link capacitors, which allows smaller capacitance to maintain the DC bus voltage. Theoretical analysis and simulation results are presented to verify this concept