Realization of a Three-Switch Leg/Phase Inverter for Nine-Phase Variable Pole– Phase Induction Machine With Phase Grouping Concepts

In this article, a three-switch leg (3SL)/phase inverter topology is realized for nine-phase variable pole–phase induction motor (9Ph-VPIM) drives. The 3SL in the proposed inverter are controlled with two nonintersecting phase-shifted references to achieve a three-level voltage excitation for each phase winding. These two nonintersecting references per leg limit the possible modulation index (MI) and may require a higher dc-link voltage. The split winding concept and the phase grouping solutions are used to enhance the MI. In the split winding concept, phase winding of the 2
n
pole machine is divided into
n
number of distinct windings and excited with the same voltage for attaining a uniform air gap flux. These coils are called cognate voltage coils (CVC). With these CVCs, different possible groupings are proposed to enhance the MI of a proposed 3SL/phase inverter. The symmetrical and efficient phase grouping solutions are analyzed and tested with an improved MI. Moreover, the proposed 9Ph-VPIM drive is controlled with carrier-based 3-
φ
space vector pulsewidth modulation to further enhance the dc-link voltage utilization. The proposed inverter will feed the effective phase by a three-level voltage with suppressed harmonics resulting in a superior torque ripple. The proposed 3SL/phase inverter fed 5-hp 9Ph-VPIM drive is validated with the experimental prototype.