In this paper, we investigate the iron loss of interior permanent magnet motors driven by PWM inverters using electromagnetic field analysis. Following 4 methods are applied: (1) Current input finite element method neglecting the carrier harmonics. (2) Voltage input finite element analysis neglecting carrier harmonics. (3) Current input finite element method with the measured armature current waveforms including the carrier harmonics. (4) Voltage input finite element method with the theoretical voltage waveforms of the PWM inverter. The calculated results are compared with the experimental ones. It is clarified that the accuracy of the calculated results are improved by considering the carrier harmonics and that the method (4) can estimate the iron loss of the IPM motor accurately before manufacturing. The variation of the iron loss components due to the driving condition is also clarified.IPM PWM

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SUMMARYA method for calculation of iron loss in rotating machines is proposed. The calculation employs the finite element method while taking into consideration the eddy currents in electrical steel sheets. First, the electromagnetic field distribution and iron loss of several types of electrical steel sheets are calculated by the proposed method, formulated as a one-dimensional model. The results are compared with those of experiments and the conventional method in order to verify the validity of the proposed method. The influence of the skin effect and magnetic saturation in the electrical steel sheets on the iron loss characteristics is also investigated. Next, the proposed method formulated as a three-dimensional model is applied to several types of rotating machines. It is shown that the skin effect is significant in the case of high-frequency harmonic fields and that direct consideration of eddy currents by the finite element method is indispensable in such cases.

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