A measurement method of minor hysteresis loss of electrical steel sheet by means of a single sheet tester

This paper investigates measurement methods of iron losses of asymmetric minor hysteresis loops of electrical steel sheets by means of a single sheet tester. As inverter-driven electric machines have been increased, consideration of harmonic iron losses is indispensable to design highly-efficient electric machines. In general, measurement of iron losses of asymmetric minor hysteresis loops has been carried out by using a fluxmeter to detect a dc component in addition to ac components measured by means of a B-coil because the asymmetric minor loops are dc-biased. However, the fluxmeter has a drift problem which results in inaccurate evaluation of harmonic iron losses. Therefore, the distorted waveform method which adopts only ac measurement is conceived. Furthermore, the dc-biased method is improved by estimating the dc components from a normal magnetization curve, which is obtained by connecting tips of symmetric hysteresis loops. In order to demonstrate their effectiveness, the iron losses of asymmetric minor hysteresis loops of non- and high permeability grain-oriented electrical steel sheets are measured up to the high flux density region.