Sizing and energy efficiency analysis of a multi-phase FSCW PMSM drive for traction application

This paper investigates the properties of multi-phase drive systems for electric propulsion systems in terms sizing and drive cycle performance. A multi-phase solution offers improved system safety due to redundancy. A 12 slot 10 poles fractional slot winding machine is chosen due to its promising characteristics in terms of short end-windings and ease for mass production utilizing pre-wound coils. The same machine can be reconfigured to be utilized both in 3-phase, using a single inverter, and in 6-phase mode using two 3-phase inverters. IGBT and SiC based inverter topologies are investigated for both 3-phase and 6-phase systems. In the multiphase mode the capacitor bank current rating can be reduced by 43.5% if PWM carrier shift is exploited. Multiple drive cycle studies are performed. For the 6-phase system a total reduction of electric machine losses of up to 4.6% and up to 3.8% inverter losses are reported.