Overview
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The eccentricity may be caused in a motor by factors including the misalignment
of the rotation axis and the center axis of the motor.
When the motor has the eccentricity, the flux density distribution and
the electromagnetic force are unbalanced, resulting in vibration and noise.
Therefore, it is important to study the effect of the eccentricity in advance.
This note presents magnetic field analysis to evaluate the electromagnetic
force on the rotor and that of the stator with the different amount of
the eccentricity. |
Electromagnetic Force on the Rotor
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Fig. 1 shows the eccentricity direction component and the component in
the orthogonal direction to eccentricity of the electromagnetic force on
the rotor. The amount of the eccentricity is set to 0, 40, and 80% of the
gap width. As the eccentricity amount increases, the eccentricity direction
component of the electromagnetic force also increases, while the component
in the orthogonal direction to eccentricity is unbalanced and the amplitude
is large. |
Electromagnetic Force on the Teeth
Fig. 2 shows the radial direction component of the electromagnetic force
on the tooth where the gap width is the smallest. The eccentricity amount
is set to 0, 40 and 80% of the gap width. And the radial direction is defined
to be positive in the direction of the circle center. Fig. 3 shows the
results for the frequency analysis of the electromagnetic force shown in
Fig. 2. As the amount of the eccentricity is larger, the variation of the
electromagnetic force is drastic, which may result in the deformation of
the stator. The increase in the higher harmonic component as indicated
with  in Fig. 3 may cause the vibration and the noise. |
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