Overview
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Along with the increasing use of highly conductive magnets as well as the
increasing needs for small-sized motors that have high-speed performance,
eddy current loss in a magnet is now an important issue.
One way to decrease the eddy current loss is to divide a permanent magnet.
This note presents the use of magnetic field analysis to evaluate the change
in the eddy current loss in the divided magnet by changing the number of
magnet divisions. |
Eddy Current Density Distribution
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Fig. 1 shows the eddy current density distribution in the magnet. For this
analysis, since the skin depth is 4 mm at 240 Hz, the eddy currents are
concentrated on the surface of the magnet in its axis direction. And as
the division of the magnet increases, the path of the eddy current is subdivided
accordingly. |
Change of the Loss in Divided Magnet
| Fig. 2 shows the eddy current loss density distribution of the magnets
and Fig. 3 shows the eddy current loss. The magnetic flux linkage to the
magnets is reduced as the number of division in the magnet increases. For
this reason, the eddy current density decreases as the number of divisions
increase and the total amount of eddy current loss is reduced. |
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