Modeling and Analysis of Novel Star-Delta Winding Configuration with Odd Slot Numbers for Reduced Space Harmonics Using Winding Function

Existing literature on 3-phase combined star-delta winding topologies only focuses on even slot numbers or conventional multiples of 6, since they emulate a 6-phase configuration with a phase difference of 30° between the star and delta connected sets. Contrarily, if a turns ratio of √3 can be achieved with proper coil and turns distribution, unconventional odd slot numbers and non-multiples of 6 can be implemented resulting in various possible design solutions with minimum spatial harmonic contents. Therefore, this paper focuses on modeling and analysis of a novel star-delta winding configuration using unconventional odd slot numbers for fractional-slot wound machines towards maximum torque density and reduced space harmonic content. Initially, a generalized analytical model using winding function theory for any slot-pole combination is presented. Furthermore, a comprehensive comparative analysis of a novel odd slot-pole combination and a conventional topology is presented in terms of spatial harmonic contents, saliency, torque density, torque ripple, rated machine efficiency and overall operating speed range.