Rotor design to reduce secondary winding harmonic loss for induction motor in hybrid electric vehicle application

Induction motor rotor designs are investigated in this paper to reduce secondary winding harmonic losses in hybrid electric vehicle (HEV) applications. The induction motor is more and more popular to use for the traction drive, but its' secondary winding harmonic losses are significantly higher than the usual when having high frequency and high power density in the HEV application. Thus, the major cause of the high secondary winding losses is analyzed and evaluated in the paper. The losses of rotor bars due to harmonic fields are calculated and analyzed for a typical eight pole induction motor by using the finite element method (FEM). Several rotor structures are proposed to decrease the harmonic losses and improve efficiency. Finally, the rotor design methods of the induction motor are compared to achieve a high efficiency and high power density based on the reduced harmonic losses, increased efficiency and output torque. The results show the secondary winding losses of the induction motor can be reduced by up to 43% when using the new rotor structure design.