Rotor design of a 7 MW interior permanent magnet wind generator considering demagnetization

Direct-drive permanent magnet (DDPM) generators have been widely adopted in the wind power applications due to the higher reliability, and lower maintenance cost, compared to that of the doubly fed induction generators (DFIG) with the gearbox [1]. However, the magnets are vulnerable to be demagnetized under the short circuit condition. Due to the reliability concerns, the demagnetization performance of DDPM generators is desired and should be analyzed in depth. Taking advantage of the high torque density, high efficiency, and compact structure, interior PM (IPM) generators with fractional slot concentrated windings (FSCWs) could be a promising option for a large-scale wind power generation system [2]. Though paper [3] has investigated the rotor demagnetization performance of IPM machines during the symmetric short circuit, it is only considering machines with distributed windings. In paper [4], demagnetization characteristics of IPM-FSCW machines with different rotor types are analyzed, but not suitable for large-scale generators.