Torque Capability Comparison of Induction and Interior Permanent Magnet Machines for Traction Applications

This paper investigates the torque generating capabilities and performance comparison of induction machines (IM) and interior-permanent magnet (IPM) machines for electric vehicle (EV) traction applications. Electromagnetic performance characteristics, such as torque, torque ripple, air-gap flux density, etc. are quantitatively compared by changing the level of electric loading. Other performance metrics such as saturation factor, power losses, efficiency, and so on, as well as the flux-weakening capability and efficiency map have also been compared. For calculations of the electromagnetic performance characteristics, 2D time-stepping finite element analysis (FEA) has been employed. It has been revealed that due to the reduction in torque components of IPM machine as a consequence of magnet demagnetization, it cannot generate toque as high as IM under overloading operating conditions. A thorough review of the literature on comparative studies on the electrical machines used in EV or Hybrid EV (HEV) applications is also included.