A modulation scheme for a split phase (six phase) induction motor is presented in this paper. For a six phase inductionmotor drive harmonics of the order 6n ±1 (n = 1,3,5 etc.,) will not contribute to the air gap flux and hence these har-monic 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 speedapplication. 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 appropriate DC-link voltages,is chosen in such away that a 12-sided polygonalvoltage space phasor combinations are achieved for each 3-phase group,independently. A modulation scheme based on12-sided polygonal voltage space phasors cancel the 6n ±1 (n = 1,3,5 etc.,) harmonic voltages from all the motor phases and hence currents due to these harmonics can not flow in the motor phases of the six phase machine. For thesame flux level of operation,nearly 11.5 % increase in modulation range is possible from this proposed drive (while stillbeing in the linear PWM range),which is more than that of a six-step over modulation region in a conventional 3-phaseinduction motor drive. The proposed drive scheme is experimentally verified,for variable speed application,using a 1.5 kW six-phase induction motor drive.
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