Switched reluctance-shark machines-more torque and less acoustic noise

This paper presents design aspects to increase torque and reduce the acoustic noise in switched reluctance machines (SRMs). The paper focuses on an axial toothed modification of the air-gap, where it is found by simple analysis that saturation is important in order to get a reduction of the generated acoustic noise. Two basic magnetic structures are analysed with and without the axial toothed modification. By different tests, it is found that the axial modified structure gives a higher magnetisation curve in both the linear and saturated case. With high saturation, a reduction of 2.6 dBA is measured on the axial modified structure. Also a classical three phase 6/4 SRM is build with the axial modification and measured results show an improvement of 70% in the unsaturated saliency ratio. Finally, it is concluded that the axial modification is a new important design aspect in electrical machines, but care has to be taken to production aspects.