Analysis of Eddy Current Losses of Segmented Nd–Fe–B Sintered Magnets Considering Contact Resistance

In large permanent magnet motors, the permanent magnet in the motor is segmented into parts in order to reduce the eddy current loss. It is reported that the insulation between Nd-Fe-B sintered magnets is possible only by contacting the segmented permanent magnets without the insulation. But the mechanism for such a phenomenon has not been clear yet. In this paper, the effect of force on the apparent contact resistance between permanent magnets is examined. The idea of contact resistance coefficient is also discussed. It is shown that the eddy current loss of segmented sintered Nd-Fe-B magnets is almost the same as the loss of the case when an insulating material is inserted between magnets.