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SUMMARY The accurate magnetic properties of electrical steel sheets are important for the development of high-efficiency electromagnetic devices. In particular, the H-coil method is a useful technique for accurately measuring magnetic field strength in a single sheet tester. Therefore, we developed a tester for magnetic field properties using the H-coil method, referred to as the stress load type single sheet tester (S-SST), and a problem was found in iron loss measurement at a high flux density of 1.6 T or more. In this paper, it is shown that the cause of this problem is the phase difference between the induced voltage in the H-coil and the B-coil. Because the phase difference makes the B-H loop slightly twisted near the tip point, the iron losses are evaluated low. Thus, we propose a method of determining the phase correction values. These values are measured in the absence of a specimen in the S-SST measurement system, and the phase correction method for induced voltage in a coil is investigated. Finally, ideal results for the correction of iron loss in nonoriented electrical steel sheets are shown. The proposed method is effective for the calibration of a single sheet tester using the H-coil method. [ABSTRACT FROM AUTHOR]

The influence of stresses on the magnetic properties of nonoriented electrical steels was studied. The dependence of iron loss on compressive stress was affected by grain size. The magnetic polarization J in strong magnetic fields such as 5000 and 10,000 A/m increased due to compressive stresses and decreased due to tensile stresses in samples with low Si content. Using Kerr-effect domain observation, it was found that the reduction in J caused by tensile stresses was attributable to residual striped domains. Magnetostriction measurements in strong magnetic fields indicated that the increase in J under compressive stresses originated from the Villari effect (inverse magnetostrictive effect) due to negative magnetostriction in low-Si materials. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 182(4): 10-18, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22320 [ABSTRACT FROM AUTHOR]