Overview
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SR motors are utilized because they have a simple construction that doesn't
use permanent magnets making them robust yet inexpensive when compared
to other motors.
However, the electromagnetic force produced by the saliency of the stator
and rotor cause vibrations and noise.
This example presents the use of a coupled magnetic field and structural
analysis to obtain the electromagnetic force of the SR motor and the resonance
of the eigenfrequency in the stator core. |
Current Density Distribution/Electromagnetic Force Distribution
The contour plot of the current density distribution when the SR motor
is at 45 degrees of rotation and the vector plot of the electromagnetic
force distribution of the stator core are indicated in Fig. 1. The frequency
components of the electromagnetic force produced at the ends of the stator
core's teeth are indicated in Fig. 2.
The electromagnetic force is large depending on the timing the current
is applied, as indicated in Fig. 1. The frequency components of the electromagnetic
force are concentrated at 66.67 HZ, as indicated in Fig. 2. |
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Eigenmode
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The eigenmode of the SR motor is indicated in Fig. 3.
The mode of deformation in the axial radial direction is near 1,660 Hz.
A large amount of vibration is generated by the resonance phenomenon of
the eigenfrequency and the electromagnetic force. |
Acceleration (Intensity) Distribution/Sound Pressure Level Distribution
The acceleration (intensity) distribution and the sound pressure level
at 1,666.665 Hz and 1,700 Hz are indicated in Fig. 4 and Fig. 5.
Acceleration larger than the resonance phenomena and a high sound pressure
level are produced at an eigenfrequency of 1660 Hz indicated in "Eigenmode"
and the electromagnetic force has frequency components (harmonic component
of 66.67 Hz). The frequency components of the electromagnetic force match
at 1700 Hz, but the acceleration and sound pressure level are smaller at
1666.665 Hz because the eigenfrequencies are different. |
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