Overview
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In recent years, the demand to reduce vibration and noise is growing with
the requirements for smaller and lighter motors. The various types of noise
range from electromagnetic noise to mechanical and fan noise. The electromagnetic
noise can be obtained using JMAG. The eigenfrequency of the stator core
is known for causing electromagnetic noise.
This example presents the use of magnetic field and structural analyses
to obtain the sound pressure distribution caused by the resonance of the
electromagnetic force and eigenfrequency of the stator core. |
Electromagnetic Force
The electromagnetic force is indicated in Fig. 1. The electromagnetic force
is the strongest at the ends of the teeth. These results indicate that
a powerful force is produced in the radial direction of the stator core.
The frequency components separated from the electromagnetic force in the
radial direction of the teeth ends are indicated in Fig. 2. The frequency
components are concentrated at 600 Hz as indicated by the results. Furthermore,
there are very few frequency components above 5,000 Hz. |
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Eigenmode
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The eigenmode around 4,200 Hz is indicated in Fig. 3. There is a mode deforming
the stator in the axial direction around 4,200 Hz. A large amount of vibration
is generated by the resonance phenomenon of the eigenmode and the electromagnetic
force. |
Acceleration Distribution
| The acceleration distribution at 600 Hz and 4,200 Hz is indicated in Fig.
4 and Fig. 5. The electromagnetic force and electromagnetic resonance of
the eigenmode indicated in Fig. 3 is produced at 4,200 Hz and the acceleration
is large at 600 Hz. Therefore, higher sound pressure can be expected. |
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Sound Pressure Level Distribution
| The sound pressure level distribution at 600 Hz and 4,200 Hz is indicated
in Fig. 6 and Fig. 7. The sound pressure level is larger at 4,200 Hz that
produces the electromagnetic resonance than at 600 Hz that has more frequency
components of the electromagnetic force, just as expected from the acceleration
distribution. |
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