Preliminary Design and Comparison of 5 Phase and 6 Phase Fault Tolerant Outer Rotor Permanent Magnet Synchronous Machines with Different Electrical Steel

In this paper, a comparison of 5 phase and 6 phase fault tolerant outer rotor permanent magnet synchronous machines (PMSM) with fractional slot concentrated winding (FSCW) is presented. The paper will show that machines with higher number of slots have less mass of active materials due to the decreased length of end windings. Further, if both conditions of outer rotor and fixed outer diameter apply, there exists only one optimal topology of FSCW from the point of view machine's torque/mass density. Finally, when comparing machines with cobalt iron (FeCo) and silicon iron (FeSi) electrical steel, the latter are cheaper, have lower iron losses and can be shorter than FeCo machines. However, when the main task is to reach high torque density per mass, FeCo machines are the better solution.