Overview
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For motors, there is a need of reducing vibration and noise.
Cogging torque is one cause of vibration and noise, so reducing cogging
torque is an important issue. And one way of reducing the cogging torque
is to skew either the rotor or the stator.
This note presents the use of magnetic field analysis to evaluate the cogging
torque of an SPM motor with the skewed stator. |
Flux Density Distribution
| Fig. 1 shows the flux density distribution at the rotation angle of 60
degrees and Fig. 2 shows the waveform of the flux density in the gap. The
flux density waveform is the average of the flux density waveforms at 3
points that are on the linear line in the axial direction as shown in Fig.
1. Fig. 1 shows that the magnetic circuit is changed by the application
of the skew. Since the skew misaligns the phases of these 3 flux density
waveforms, the variation of the averaged flux density waveform is small.
So it is expected that the cogging torque may be reduced by applying the
skew. |
Closeup |
Closeup |
Cogging Torque
Closeup |
Fig. 3 shows the cogging torque waveform of the SPM motor with and without
the skewed stator.
The peak value of cogging torque of the skewed stator is reduced by about
60 percent when compared to that of the non-skewed stator. |
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