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The eddy current loss of magnets cannot be ignored with the increasing
use of highly conductive magnets as well as the need for faster and smaller
motors. One way to decrease the eddy current loss is to use divided magnets.
Ways to reduce the eddy current loss by dividing magnets can be examined
using analyses.
This example presents the use of a magnetic field analysis to obtain the
variations of eddy current loss in magnets by the number of divisions using
the gap flux boundary condition. The analysis results can be obtained more
efficiently reducing the time required for the standard transient response
analysis by using the gap flux condition. |
Variations of Loss by Magnet Divisions
The eddy current loss of the magnets is indicated in Fig. 1 and the eddy
current loss density distribution is indicated in Fig.2.
The loss is large at 2,880 Hz as indicated by Fig. 1. The higher loss is
caused by the slot harmonic components determined from the rotation speed
times the number of slots. The eddy current loss decreases as the number
of magnet divisions increases as indicated by Fig. 1 and Fig. 2.
The magnetic flux linking to each divided magnet is reduced by increasing
the number of divisions. Therefore, the eddy current density of each divided
magnet is reduced and the total eddy current loss decreases. |
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Eddy Current Density Distribution of the Magnets
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The eddy current density distribution in the magnets at 2,880 Hz is indicated
in Fig. 3. The eddy currents are reduced by dividing the magnets. |
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