Abstract:Big amplitude sub-harmonics and higher order harmonics with same winding coefficient as fundamental component, especially the harmonics with same fundamental winding coefficient, different direction rotation, big amplitude and small pole number difference, all exists in the fractional-slot concentrated winding permanent magnet synchronous machine(PMSM) with few slots and multiple poles. These can lead to a strong armature reaction harmonic field, consequently with a significant harmonic leakage reactance and overall leakage inductance. Further, it can be found that the fundamental component magnetizing inductance is much lower than that of the traditional short pitch distributed winding PMSM, and the leakage inductance is bigger than the magnetizing inductance. Then the inductance calculation formulas are derived for such machines with varied number of slots and poles under ideal condition. The results show that the formula for the fundamental component of armature reaction magnetizing inductance is same as that for the traditional AC machines. However, the formulas for the armature reaction overall inductance and the harmonic leakage inductance are changed.
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