Analysis of Permanent Magnet Demagnetization Accounting for Minor Curves

The paper presents a method accounting for a partial demagnetization of isotropic permanent magnets at elevated temperatures and maximum loads in the application. The method incorporates two coupled finite-element models for the magnetization and application. The magnetization model is employed to analyze the true distribution and orientation of the magnetization vector in the magnet. Then the application model with the imported magnetization provides the demagnetizing field along the magnetization vector at the given temperature and current. The recoil line model is used to recalculate the magnetization vector for the operating points fallen below the knee of demagnetization of the major or minor B-H curve. The corrected magnetization table is imported back into the application model to assess the flux reduction. The method is applied to analyze the demagnetization in the magnetically biased transformer, brush, and brushless motors.