Application Catalog
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| 40 - Cogging Torque Analysis of an SPM Motor <DP> |
Overview
Closeup |
Cogging torque is produced by the interaction between the permanent magnet
and the stator core when the rotor rotates with no current flow.
The cogging torque prevents the smooth rotation of the rotor, which may
lead to vibration and noise. So the evaluation of the accurate cogging
torque can be an important issue.
The period of the cogging torque is determined by the number of poles and
slots, so they are significant factors for evaluating cogging torque.
This note presents the use of magnetic field analysis for evaluating the
cogging torque of an 8-pole, 9-slot SPM motor, which has relatively small
period of the cogging torque. |
Cogging Torque Waveform
Closeup |
Fig. 1 shows the cogging torque waveform. As shown in the waveform, the
amplitude is about 5.5*10-5Nm. A period of the cogging torque is 5 degrees because the motor in use
has 8 poles and 9 slots. |
Flux Lines
| Fig. 2 shows the flux lines at the rotor angles A, B, and C indicated in
Fig. 1. The flux lines at the angle A are symmetric, whereas the lines
at the angles B and C are not symmetric. This asymmetry generates the cogging
torque. |
Closeup |
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Updated: 2011-01-17
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