Performance analysis of fractional slot wound PM-motors for low speed applications

This paper introduces a performance comparison of different permanent magnet motor structures equipped with fractional slot windings in which the number of slots per pole and phase q < 1. Such a PM machine is an attractive solution for low-speed applications in which copper losses often dominate as iron losses are of less importance. It was in the authors interest to have a low speed motor to a specific application, in which high torque and 45 kW output power at 420 rpm can be achieved using a restricted motor volume. These demands lead to study multi-pole machines with fractional slot windings. One of the designs studied was verified via a prototype machine.