Overview
Consequently, in order to accurately evaluate a motor that has skew applied, one needs a magnetic field analysis simulation that uses the finite element method (FEM), which can account for a detailed 3D geometry, instead of studies that use the magnetic circuit method or a 2D magnetic field analysis.
This Application Note presents the use of a magnetic field analysis to obtain the flux density distribution, cogging torque, and induced voltage of an SPM motor that has skewed magnetization applied to its magnet.
Magnetic Flux Density Distribution
Cogging Torque Waveform
The peak value of the cogging torque is reduced by approximately 90% when skew has been applied to the magnet.
Induced Voltage Waveform
The induced voltage waveforms of the U-phase at skew angles of 0 deg and 30 deg are shown in fig. 3, and the frequency components of the U-phase’s induced voltage waveforms are shown in fig. 4.
The high frequency components are reduced when skew is applied to the magnet. The ratio taken up by the fundamental frequency of 60 Hz out of the total frequency components is 71% with a skew angle of 0 deg and 82% with a skew angle of 30 deg. According to these results, the induced voltage waveform is smoother at a skew angle of 30 deg than at an angle of 0 deg.