Recently, various kinds of exciting conditions are applied to transformers, motors etc. with the development of power electronics technology. The use of iron core under dc-biased magnetization generates a distorted asymmetrical hysteresis loop, and the iron loss under dc-biased magnetization is increased compared with sinusoidal excitation. Usually, dc-biased magnetic properties of electrical steel sheets have been evaluated by using a ring specimen, because a dc component of magnetic field strength, H{sub}(dc), can be simply obtained from a dc exciting current applied, if a mean magnetic path length is given appropriately. A dc component of flux density, △B, can be measured by using a flux meter. However, in the case of an ordinary single sheet tester (SST) using an H coil method, it is not easy to accurately measure H{sub}(dc). Moreover, the magnetic coupling occurs between the ac exciting coil and the dc exciting coil due to the short distance between both coils is also the problem for accurate measurement.
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