Investigation of a Six-Phase Interior Permanent Magnet Synchronous Machine for Integrated Charging and Propulsion in EVs

Merits such as reduced weight, overall and operational costs of the electric vehicle (EV) while providing level 3 charging capability, are propelling research on integrated charging (IC) technology for EVs. Since the same interior permanent magnet synchronous machine (IPMSM) is used during IC and traction conditions, it is important to understand the behavior of the machine during these conditions and optimally design the machine. Hence, firstly, this paper presents a case study on performance of a laboratory 3-phase IPMSM under IC and traction conditions. Thereafter, understanding the challenges such as low magnet operating point, losses and torque oscillation in 3-phase IPMSM during IC, a 6-phase IPMSM with an unconventional configuration is investigated to yield traction characteristics like that of the 3-phase IPMSM and mitigate challenges during IC. In the process, mathematical model of the 6-phase IPMSM is developed employing the dq-axis theory. The developed model is then employed to exclusively derive the relation between various per-unitized machine parameters to obtain optimal performance under IC and traction conditions. Thereafter, a novel bottom-up machine design methodology based on maximum-torque per ampere control technique is proposed to design a 6-phase IPMSM that will yield desired performance under traction and IC conditions. Finally, a 6-phase IPMSM has been designed using the proposed design methodology and its performance has been investigated under traction and IC conditions through a developed prototype and electromagnetic model of the machine in conjunction with finite element analysis.