Induction Machine Drive Design for Enhanced Torque Profile

This paper presents a design philosophy to design an induction machine (IM) based drive with minimized torque ripples. Inverter injects the time harmonics into the IM. Slots and winding formations of the machine are the cause of space harmonics in the air-gap flux density. The interaction between time harmonics and space harmonics inside the air-gap is responsible for ripples in the electromagnetic torque of the IM. An IM model has been derived to incorporate the effect of machine design parameters as a ripple producing cause in the torque response. Harmonics in the flux density wave, due to distribution of winding around air gap periphery and due to slot permeance effect, have been considered together and modeled as ripple producing cause in the torque response. Classical approach of IM modeling through mutual inductance calculation has been adopted. In order to minimize large torque ripples mathematical model has been subjected to a heuristic-based optimization technique by considering the number of slots and winding distribution as variables. Torque ripple of the optimized feasible machine is found to be negligibly small. Later, performance of the optimized feasible machine has been verified using the finite element model of the machine.