Demagnetization Performance of a 7 MW Interior Permanent Magnet Wind Generator With Fractional-Slot Concentrated Windings

High reliability is one of the most important requirements for large-scale permanent magnet (PM) wind generators. However, the magnet suffers partially irreversible demagnetization due to the material property, especially under short-circuit conditions. To improve fault-tolerance capability and torque density, fractional-slot concentrated windings (FSCWs) have been adopted in wind generators. However, the rich harmonics of magnetomotive forces make the demagnetization characteristics different from that of generators with distributed windings. In this paper, the partial demagnetization performance of a 7 MW interior PM wind generator with FSCWs is investigated, under the symmetric short-circuit condition. In addition, influences of slot-pole combinations and rotor types are analyzed to improve the antidemagnetization capability. The transient magnetic behavior is evaluated by the finite-element analysis.