Harmonic impact on rotor losses in fault-tolerant interior permanent-magnet machines

Fractional-slot permanent-magnet (FCSPM) machines offer several advantages, but they suffer from the high content of space harmonics in the air-gap magnetic motive force (MMF) distribution. The MMF space harmonic amplitude and frequency depend on the particular combination of numbers of slots and poles. Such harmonics induce losses in the rotor since they are not synchronous with the rotor speed. The aim of this paper is to analyze the MMF distribution in the air-gap and calculate the rotor eddy current loss for two fault-tolerant interior permanent-magnet (FT-IPM) machines. Meanwhile, the efficiency has been predicted at different operating conditions. Both machines are built for verification.