Application of a Method Utilizing an Electromagnet to the Measurement of the Magnetic Properties of Non-Oriented Electrical Steel Sheets

When nonlinear magnetic phenomena in electromagnetic devices are investigated by means of numerical methods of analysis, it is obligately to take account of magnetic properties of magnetic materials used in the devices. The magnetic properties to be prepared should be dc-like to keep uniform magnetization avoiding the eddy current effect in a specimen, and have dataset with enough excitation as higher as possible to stabilize the nonlinear magnetic field analysis. In order to measure magnetic properties of electrical steel sheets, a single sheet tester is standardized in the IEC (International Electrotechnical Commission) and the JIS (Japanese Industrial Standards), and is widely used because of easy preparation of specimen. In case of permanent magnets, an electromagnet is used for excitation. It is also used in a VSM (vibrating sample magnetometer) system. The electromagnet can realize the higher excitation at very low frequency. However, demagnetizing fields are intrinsically generated due to contact of different materials between specimen and pole piece. They should be corrected to obtain accurate magnetic properties. In this paper, a method utilizing an electromagnet was applied to the measurement of the magnetic properties of non-oriented electrical steel sheets to extend the application area of the method. The effect of the waveform control on the measurement accuracy was described. It was demonstrated that a sinusoidal flux condition is required to get the sufficient measurement accuracy at high flux density region. Furthermore, the results were compared with those obtained from an ordinary single sheet tester for verification.