Overview
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When a motor is constructed, the diameter of the stator becomes uneven
because of fabrication errors and shrink fitting. It is advantageous to
investigate the uneven diameter of the stator because it largely effects
the cogging torque.
This example presents the use of a structural and magnetic field analysis
to obtain the cogging torque with stator teeth that have an uniform and
varying diameter based on the displacement obtained with a stress analysis. |
Displacement of the Teeth
The displacement of the teeth is indicated in Fig. 1 and a contour plot
of the displacement is indicated in Fig. 2. When the thickness of the frame
is even, the displacement is even in all of the teeth. However, if the
thickness of the frame is uneven, the displacement is also uneven. The
displacement is larger in the thicker parts of the frame. The uniform thickness
of the frame is indicated as even and the varying thickness of the frame
is indicated as uneven.
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Cogging Torque
| The cogging torque waveform is indicated in Fig. 3 and the frequency components
of the cogging torque are indicated in Fig. 4, Fig. 5, and Fig. 6. The
amplitude of the cogging torque is larger for an uneven frame when compared
to an even frame. The amplitude is larger with an uneven frame for the
frequency components of cogging torque at 720 Hz and the frequency at 120
Hz that originates in the indents of the teeth every 90 degrees. |
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