Identification of the Magnetic Flux Density Dependence of Effective Conductance in Cauer Circuit Representation

The low-frequency magnetic field induced by the eddy current in a silicon steel sheet can be approximated by the product of a coefficient g and the time derivative of the magnetic flux density dB/dt. The coefficient g is often represented as an equivalent conductance in the circuit model. In some previous research, the conductance g is often assumed to be a constant. However, in practice, the conductance depends on the applied magnetic flux density. In this research, we developed a method to identify the magnetic-flux-density-dependent conductance using the measured eddy-current loss. The eddy-current loss is affected by external factors, such as temperature and mechanical stress. The mechanical stress commonly exists in the magnetic materials in a device and may affect the device performance. Therefore, we selected the mechanical stress as an external factor to validate the accuracy of the proposed identification method. A Cauer circuit with the identified flux-dependent conductance under various compressive stress conditions was used to analyze the AC magnetic properties of the silicon steel sheet. The iron loss evaluation was improved for the rolling, transverse, and 45° directions of the silicon steel sheet by introducing the flux-dependent conductance.