Analytical calculation of iron losses reduction for interior permanent magnet synchronous motor

Interior permanent magnet motors are widely applied to the industry, especially to the electric vehicle field that requires high power and high efficiency. For the limited space for the motors used in electric vehicle, it is difficult to cool them, which makes losses reduction to be a crucial target. As the main part of losses, iron loss is caused by the magnetomotive forces of permanent magnet and armature. With uniform air-gap, the flux density in the motors includes many harmonics, which increases iron losses. Some papers used pole eccentricity to optimize flux density waveforms and decrease the harmonics by finite element method (FEM). Actually, analytical calculation which points the influence factors for reduction of losses is more meaningful for designers. This paper presents a general analytical calculation to optimal rotor shape, which is effective to decrease iron losses. Considering the magnetomotive force of armature is different between distributed winding and concentrated winding, this paper also investigates the methods to decrease iron losses according to winding types.