Abstract
Compared to conventional distributed winding configurations, the fractional-slot non-overlapping (concentrated) windings exhibit advantages such as short end-winding length, high copper packing factor (particularly with segmented stator structure), low cogging torque, good field weakening capability owing to relatively large d-axis inductance, and better fault tolerant capability due to low mutual inductance. However, one of the key problems of employing concentrated windings in Permanent-magnet Synchronous Machines(PMSMs) is the high eddy-current losses in rotor magnets and/or rotor iron due to the presence of a large number of lower and higher order space harmonics in the stator Magneto-Motive Force(MMF). These MMF harmonics also result in other undesirable effects, such as acoustic noise and vibrations, and localized core saturation which tend to reduce reluctance torque. This paper reviews the current state-of-the-art of the MMF harmonic reduction techniques for concentrated winding configurations in PMSMs, including winding split and shift, delta-star connected windings, multiple 3-phase windings, multilayer windings, uneven turn numbers, and stator flux barriers. Their concepts, advantages and disadvantages are presented and assessed.
Highlights
Permanent-magnet Synchronous Machines(PMSMs) exhibit high torque density and high energy efficiency over a wide operation range, due to the presence of the permanent magnets[1,2]
With magnets mounted on the rotor surface, Surface-mountedPermanent-magnet Machines (SPMs) produce torque by the interaction of the magnetic field contributed by permanent-magnets with the armature reaction field produced by the stator magnetic-motive force (MMF)
The concentrated winding configurations are of potential to be employed in InteriorPermanent-magnet Machines (IPMs), given that the lower and higher order space harmonics in the stator MMF can be suppressed to a desirable level
Summary
Permanent-magnet Synchronous Machines(PMSMs) exhibit high torque density and high energy efficiency over a wide operation range, due to the presence of the permanent magnets[1,2]. Chen et al.: Magnetomotive Force Harmonic Reduction for Fractional-Slot Non-Overlapping Winding Configurations in PMSM incur high eddy current loss[36] This can further leads to a high rotor temperature at high speeds, and the rotor magnets will suffer from a high risk of irreversible demagnetization. The concentrated winding configurations are of potential to be employed in IPMs, given that the lower and higher order space harmonics in the stator MMF can be suppressed to a desirable level This can increase IPMs’ reluctance torque production, reduce the eddy-current losses in both rotor magnets and rotor iron, and suppress acoustic noise and vibrations. Both SPMs and IPMs can greatly benefit from the reduction of the stator MMF harmonics in the concentrated windings. This paper reviews the current state-of-the-art of MMF harmonic reduction techniques
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