Investigation of Eddy Current Loss in Divided Nd–Fe–B Sintered Magnets for Synchronous Motors Due to Insulation Resistance and Frequency

In this paper, we investigate eddy current loss in divided Nd-Fe-B sintered magnets for synchronous motors, from both sides of measurement and finite element analysis. First, the basic experiments with an exciting coil and divided magnets are carried out. The results are compared with the 3-D finite element analysis to clarify the effects of insulation resistance between divided magnets, number of magnet divisions, and frequency. Next, a permanent magnet synchronous motor is analyzed to understand the eddy current generation in the magnets applied to the motors. It is clarified that the effect of the eddy current loss reduction by the magnet division is weakened in the case of high frequency harmonic magnetic fields. The critical insulation resistance between the divided magnets is also clarified.