Investigation of Interior Permanent Magnet Motor With Dampers for Electric Vehicle Propulsion and Mitigation of Saliency Effect During Integrated Charging Operation

Power electronics and motor drive components existing in a conventional electric vehicle (EV) drivetrain employed to propel the EV can also be used to charge the battery under level 3 fast charging capacity. This integrated battery charging technology can be realized by employing the winding inductances of the three-phase interior permanent magnet synchronous motor (IPMSM) used for propulsion as line inductors while charging the EV's battery pack. The difference in the d- and q-axis inductances in the IPMSM offers unbalanced Thevenin impedances as viewed from stator terminals. This causes the voltages across the stator windings to become unbalanced when balanced three-phase currents synchronized with the grid utility voltages are forced into the three armature phases during charging. This paper first presents a case study employing a conventional laboratory IPMSM to illustrate the unbalanced phase winding impedance during an “emulated integrated charging” operation. Thereafter, the authors derive motivation to design and analyze an IPMSM with dampers in the rotor for propulsion and mitigation of the saliency effect, that is, the effect of unequal armature phase impedance at standstill during integrated charging. A novel design approach is presented and employed to design an IPMSM with dampers. Performance of the designed IPMSM with dampers is compared to that of the conventional IPMSM under both integrated charging and traction conditions. The proposed design is also validated experimentally using a laboratory IPMSM with dampers.