Development of Measuring Equipment of DC-Biased Magnetic Properties Using Open-Type Single-Sheet Tester

The use of an iron core under dc-biased magnetization generates distorted asymmetrical hysteresis loop, and the iron loss is increased compared with that under sinusoidal excitation. Although the accurate measurement of magnetic properties under dc-biased magnetization is important for the estimation of iron loss of apparatuses, such as a reactor for an inverter which is operated under dc-biased condition, the reports of measurement of such magnetic properties are few. This is mainly because the measuring method of such magnetic properties and the method for accurate evaluation of dc-biased magnetization are not established yet. In this paper, a measuring system of magnetic properties of electrical steel sheet under dc-biased magnetization using an open-type single-sheet tester (SST) and a Helmholtz coil is developed. The newly developed system has an advantage that the interaction between ac and dc excitations is negligible, then the control is easy compared with the usual technique using a ring core or SST having both ac and dc exciting windings. It is shown that the increase of iron loss of 6.5% Si-Fe sheet due to the dc bias is larger than that of usual nonoriented silicon steel sheet.