Magnetic Circuit Analysis /Reduction in Eddy Current by Splitting Magnets

  • SPM Motor
  • IPM Motor
  • Eddy Current for Large Motor
  •  DRM Uniform Magnetic Field Circuit
  • Magnetic Fields for Plasmas

Reduction in Eddy Current by Splitting Magnets

Reduction in eddy current by splitting magnets

As a countermeasure to eddy current, it is effective to split magnets. We further investigated split magnets. The eddy current loss was compared for a motor with magnets not split and with the magnets split into 6 pieces as in Figure (a). There were four test materials: C1020 copper, A7075 aluminum, SUS304 stainless steel, and N36UH magnets. The test pieces were 50x50x10 mm, the strength of the AC magnetic field was ±12.3 kA/m (±154 Oe) and the frequency was 2000 Hz.

Figure (b) shows the relationship of the eddy current loss with whether or not the magnets were split. With copper and aluminum, which have comparatively weak resistance, the loss is larger when the magnets are split. This is due to the surface effect of eddy current. When the test piece is larger or the frequency is high, the eddy loss due to splitting increases.

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Magnets split into 6 and not split

Figure (a) Magnets split into 6 and not split

Comparison of eddy current loss

Figure (b) Comparison of eddy current loss


Figure (c) shows the result of bringing the split test material in contact without insulation and measuring the eddy current loss. A comparison was made with items completely insulated between layers. It was found that splitting had an effect for all the materials, regardless of the insulation between layers. When producing split magnets, there is no need for a process to completely insulate between layers, for example with paint.

Click the thumbnail for the large figure.

Relationship of the eddy current loss with whether or not the magnets are split

Figure (c) Relationship of the eddy current loss with whether or not the magnets are split

  • SPM Motor
  • IPM Motor
  • Eddy Current for Large Motor
  •  DRM Uniform Magnetic Field Circuit
  • Magnetic Fields for Plasmas

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