Analysis and experimental evaluation of harmonic leakage inductance for polyphase PM machines having close slot and pole combinations

For polyphase fault-tolerant fractional-slot concentrated winding (FSCW) permanent magnet (PM) machine, harmonic leakage inductance plays a significant role in increasing winding inductance and reducing fault currents. For conventional distributed winding (PM) synchronous machine, harmonic leakage coefficient curves, which are particularly required in magnetic-circuit-based design process, are available for machine designers. However, similar harmonic leakage coefficient curves for FSCW PM machines having close slot and pole combinations receive few attention. Since high-order magneto motive force (MMF) component rather than fundamental MMF component is utilized in FSCW machine, harmonic leakage inductance could be several times larger than main inductance. This fact makes it rather significant to normalize harmonic leakage coefficient calculation. This paper aims to investigate harmonic leakage coefficient calculation of polyphase FSCW PM machines having close slot and pole combinations by making use of winding harmonic analysis and analytical modeling.