Overview
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Reactors are used in a variety of electric power system. An important concern
for reactors is the noise caused by resonance phenomena of the electromagnetic
force and eigenfrequency.
The sound pressure can be evaluated with a structural analysis using the
electromagnetic forces obtained from magnetic field analysis as the excitation
force.
This note presents how sound pressure from a vibrating reactor can be obtained
when a structural spacer is removed. |
Electromagnetic Force Distribution
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Figure 1 shows the distribution of the electromagnetic forces.
Since the material of the spacer is a non-magnetic material, the magnetic
circuit does not change regardless of spacer removal, so electromagnetic
force distributions will be the same whether the spacer is removed or not.
Figure 1 shows that the electromagnetic force is concentrated in the gap.
This is due to the difference in the permeability of the core material
and the spacer. |
Eigenmode
| Figure 2 shows the eigenmode at the frequency approximately 20 kHz. When
the spacer is removed, the structural symmetry of the sides is corrupted,
and this leadds to deformation at the top of the reactor. Since the electromagnetic
force is concentrated in the gap, sound pressure and vibration are expected
to increase by a removal of the spacer. |
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Acceleration Distribution
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Figure 3 shows the distribution of the acceleration. Since the electromagnetic
force distribution does not change by the removal of the spacer, the difference
in the eigenmode must be the cause of the difference in the acceleration
distribution. The removal of the spacer increases the acceleration, and
particularly the vibration increases near the gap. |
Sound Pressure Distribution
| The distribution of sound pressure is shown in the Figure 4. Removal of
the spacer has a large effect on the sound pressure distribution. If all
of the spacers are in place, the core material vibrates up and down. If
one spacer is removed, vibration takes place in the gap in the direction
longitudinal to the core, and hence the distribution is dispersed. The
sound pressure level is high without the spacer due to the larger vibration. |
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