抄録
This paper examines the cogging torque of permanent magnet (PM) motors resulting from the asymmetry property of the magnetic poles. Starting from the theoretical analysis of motor internal magnetic energy, we indicate that the pulsation number per revolution of the above-mentioned cogging torque component can be expressed as the multiple of the number of slots. We show the condition that the above-mentioned cogging torque component is generated as the relation between the MMF spatial distribution mode and the motor design parameters; the number of poles and the number of slots.
We propose a motor quality prediction method from the viewpoint of the cogging torque resulting from the asymmetry property of the magnetic poles before the rotor is set into the stator—the magnetic flux density around the rotor is measured first, the measured value is squared, and then the componential analysis is made by DFT. The cogging torque amplitude is predicted by the content rate of the causal asymmetrical component. The effectiveness of the proposed method was confirmed experimentally. The verification motor has 32 poles and 36 slots, which is sensitive to the asymmetry property of the magnetic poles.
