Multi-Phase DC-Decoupled Inverter Topology to Enhance Performance of Electronic Pole Changing Induction Motor Drive

The electronic-pole/mode changing (E-PC) mechanism includes wide flexible speed-torque ranges by operating induction motor drive (IMD) in different pole-phase combinations/modes. To have varied pole-phase combinations in IMD an inverter employing diverse pulse-width-modulation (PWM) strategies is required. The diverse PWM strategies result in common-mode-voltage (CMV) at the inverter. The inverter's CMV produces space-harmonics in IMD stator periphery. The space-harmonics are attributed to the common-mode-current produced by inverter's CMV. Thus, by inverter driven E-PC operation in IMD, a predominant torque ripple exists especially during high-pole modes. Moreover, E-PC IMD grieves flux and torque distortions due to improper stator-core magnetization and demagnetization during pole-changeover. Consequently, E-PC mechanism significantly affects drive dynamics. Therefore, the inverter's PWM should minimize the CMV at its individual operating modes and enable gradual pole-change in IMD during mode transition operation. In addition, the inverter should be less complexity in operation with optimum switch count. Hence, the paper proposes a multi-phase DC-decoupled inverter topology with hybrid-PWM technique considering the above-mentioned key points. The paper also gives switching-function analysis to verify inverter's CMV and finite-element analysis to examine the pole-changing behavior in IMD. The realization studies of the system are carried out in the ANSYS environment and elucidated experimentally.