Design guidelines for fractional slot multi‐phase modular permanent magnet machines

This study presents the design considerations for a fractional slot multi‐phase modular permanent magnet (PM) machine with single‐layer concentrated windings. The winding factors for various slot/pole number combinations are calculated to identify the optimal slot/pole number combinations for different phase numbers. In addition, the electromagnetic performance influenced by flux gaps (FGs), such as air‐gap magneto‐motive force, back‐electro‐motive force, cogging torque, on‐load torque and torque ripple etc. are comprehensively investigated by using the two‐dimensional finite element (FE) method. Several general rules with respect to the influence of FGs on multi‐phase modular PM machines performance are established. The prototypes of modular PM machines are built and the FE results are validated with experiments.