The influence of the shearing process on the iron loss of non-oriented electrical steels with thicknesses of 0.20-0.50 mm was investigated. The deterioration of material iron loss was lesser in thinner steel sheets. The distribution of the increase in hardness near the sheared edge was almost half of the sheet thickness for all tested steels. Therefore, applying thinner steel sheets for the motor core may decrease the iron loss deterioration from the punching process. This argument was supported by measuring the iron loss of a model IPMSM using steels with different thicknesses and calculating the motor iron loss through FE analysis. The magnetic properties of narrow pieces corresponding to the width of the motor's teeth and yoke were shown to be important and useful to estimating the motor iron loss more accurately.
Si-gradient steel sheet, which has a silicon concentration gradient in the sheet thickness direction, manufactured by the chemical vapor deposition siliconizing process, possesses unique magnetic properties. In this paper, the magnetization behaviors of single crystals of Si-gradient steel sheet are investigated in the <100> and <110> directions, comparing with Si-homogeneous steel sheet, in order to clarify the magnetization mechanism. The internal stress of Si-gradient steel sheet was evaluated. The induced magnetic anisotropy which arising according to the magnetoelastic effect is considered to play an important role in the magnetization process of Si-gradient steel sheet. The reduction of eddy current loss can be explained by the effect of the magnetic flux concentration at the sheet surface resulting from the internal stress. C⃝ 2015 Wiley Periodicals, Inc. Electr Eng Jpn, 193(2): 18-29, 2015; Published online in Wiley Online Library (wileyonlinelibrary.com).
Power losses of 6.5% silicon steel sheets under PWM (Pulse Width Modulation) voltage excitation were examined. The PWM wave was composed of a 50Hz fundamental wave, a 16kHz carrier frequency wave and some other higher harmonics. It was found that the power losses of the inductor cores were much larger than those of the transformer cores when the cores were driven by a PWM inverter, although such a great difference was not observed under sinusoidal voltage excitation. Power losses of the inductor made of 6.5% silicon steel sheets and conventional grain oriented 3% silicon steel sheets under PWM voltage excitation were also investigated It was found that the power losses of the inductor made of 6.5% silicon steel sheets were reduced by more than 30% compared to those of the inductor made of grain oriented 3% silicon steel sheets. This was because the grain oriented 3% silicon steel sheets had higher losses at higher harmonics found in the PWM excitation. Therefore, it was clearly shown that 6.5% silicon steel sheet was a suitable material for the inductor under PWM voltage excitation.
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