A novel modulation scheme for a six phase induction motor with open-end windings

A modulation scheme for a six phase induction motor is presented in this paper. For a six phase induction motor drive harmonics of the order 6n ±1(n=1,3,5 etc.,) will not contribute to the air gap flux and hence these harmonic currents are limited by the stator impedance only. So harmonic filters are needed for the suppression of these 6n ±1(n=1,3,5 etc.,) high amplitude harmonic currents, when a six phase induction motor is used for variable speed application. In the proposed scheme, a modulation technique to eliminate the 6n ±1(n=1,3,5 etc.,) harmonic currents, without the need for harmonic filters, from the stator phases of a six phase induction motor drive is explained. An open-end winding drive configuration with DC link voltages, chosen in such away that a 12-sided polygonal voltage space phasor combinations are achieved for each 3-phase group, independently. A modulation scheme based on 12-sided polygonal voltage space phasors will cancel the 6n ±1(n=1,3,5 etc.,) harmonic voltages from all the motor phases and hence currents due to these harmonics will not flow in the motor phases of the six phase machine. The proposed drive scheme is experimentally verified, for variable speed application, using a 1 HP six phase induction motor drive.