Comparative analysis of rotor losses in high-speed permanent magnet machines with different winding configurations considering the influence of the inverter PWM

Due to development in fields of materials and power electronics, use of high-speed electrical machines has boosted significantly in recent decades. They are widely used in number of applications, such as electrically assisted turbochargers, flywheel energy storage systems, spindle applications, turbo molecular pumps, micro gas turbines. In applications where high efficiency and high power density are required, the most suitable machine type for high-speed operations is a permanent magnet (PM) machine. In this paper the performance of several different topologies of high-speed PM machines required for use in a micro-gas turbine application are evaluated. Different winding topologies, retaining sleeve materials and magnetization patterns are considered, where the main criterion for the machine performance are eddy current losses in the rotor. Influence of time harmonics in stator currents caused by the inverter Pulse Width Modulation (PWM) is incorporated in the calculation.