Overview
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Eccentricity may occur in the motor due to a misalignment of the rotation
axis and the center axis of the motor.
Evaluating the effects of eccentricity is often requested because vibration
and noise in the motor due to an unbalanced magnetic flux density distribution
and electromagnetic force caused by eccentricity.
This example presents the use of a magnetic field analysis to obtain the
torque waveform and effects on the electromagnetic force acting on the
stator for an SPM. |
Torque Waveform / Magnetic Flux Density Distribution
| The torque waveform with and without eccentricity is indicated in Fig.
1. The magnetic flux density distribution with a rotation angle of 180
degrees at the largest difference in the position of the rotor is indicated
in Fig. 2.The torque fluctuates after one rotation of one period when eccentricity
is applied, as indicated in Fig. 1. The magnetic flux density distribution
increases in the stator core along the direction that eccentricity occurs,
as indicated in Fig. 2. As these results show, the difference in the magnetic
flux density distribution caused by eccentricity affects the torque waveform. |
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Electromagnetic force acting on the stator
| The eccentricity direction component of the electromagnetic force acting
on the stator is indicated in Fig. 3. The orthogonal direction component
of the eccentricity is indicated in Fig. 4. Each of the components has
an electromagnetic force waveform with one rotation that is one period
due to eccentricity. Vibration and noise can be caused by the electromagnetic
resonance if the frequency component of the electromagnetic force acting
on each part is around the eigenmode of the motor. |
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