Influence of local magnetic saturation on iron losses in interior permanent magnet machines

Abstract

Interior PM (IPM) machines can have severe local magnetic saturation especially in the rotor iron region above the PMs and the stator tooth-tips. In this paper, the influence of local magnetic saturation on the iron losses is comprehensively investigated in IPM machines accounting for the influence of the slot/pole number combinations. Due to local magnetic saturation, the tooth-tips have much higher iron loss density than the other parts of stator. The iron loss density of the rotor iron regions above the PMs is also high. Also both the iron losses in the tooth-tips and the rotor iron regions above the PMs remain high even when IPM machine is under deep flux weakening. It is found that fractional slot machines have higher local magnetic saturation and iron losses than the integer slot machines. The IPM machine will exhibit higher local magnetic saturation than the machine having the same slot number but lower pole number.