An inherent drawback of permanent magnet synchronous motors is the torque ripple caused by stator and rotor anisotropy and non sinusoidal distributions of the PM flux-density and stator mmf. A classical method to minimise the torque ripple consists in skewing the stator or the rotor. However such a method causes difficulties in motor manufacturing and it is generally avoided. Also alternative techniques as fractional-slot windings, diverse pole widths, dummy slots or teeth cause manufacturing troubles or are well-suited only for low power motors. A technique based on an appropriate shifting of identical width rotor poles is presented in this paper. It can be applied to both surface-mounted PM and interior PM sinusoidal-fed motors of any size. Hints to design rotors of any number of pole pairs are also given. The results achieved by the proposed technique are verified by a finite element analysis of the motor performance and their validity is confirmed by experimental tests on a prototype.
Reducing Torque Ripple in PM Synchronous Motors by Pole Shifting
BIANCHI, NICOLA;BOLOGNANI, SILVERIO
2000
Abstract
An inherent drawback of permanent magnet synchronous motors is the torque ripple caused by stator and rotor anisotropy and non sinusoidal distributions of the PM flux-density and stator mmf. A classical method to minimise the torque ripple consists in skewing the stator or the rotor. However such a method causes difficulties in motor manufacturing and it is generally avoided. Also alternative techniques as fractional-slot windings, diverse pole widths, dummy slots or teeth cause manufacturing troubles or are well-suited only for low power motors. A technique based on an appropriate shifting of identical width rotor poles is presented in this paper. It can be applied to both surface-mounted PM and interior PM sinusoidal-fed motors of any size. Hints to design rotors of any number of pole pairs are also given. The results achieved by the proposed technique are verified by a finite element analysis of the motor performance and their validity is confirmed by experimental tests on a prototype.Pubblicazioni consigliate
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