Estimation of Local Demagnetization in Ferrite Magnet Using Pinching-Type Sigmoid Function Based on Gradient Method (P-SiGrad)

In recent years, the development of electric vehicles (EVs) is being actively pursued. Several permanent magnet synchronous motors are installed in EVs. Revealing the magnetization state inside PMs is essential at the early design stage to improve the manufacturing quality of permanent magnet (PM) motors. Therefore, a method known as SiGrad has been developed by the authors to numerically estimate the magnetization distribution using the magnetic flux density measured around PMs. Consequently, the effective performance of SiGrad in the PM estimation with the homogeneous magnetization distribution is demonstrated. However, the performance of the estimation of the PM with inhomogeneous distribution in the demagnetized region is not investigated. In this study, the applicability of SiGrad to demagnetized magnetization estimation is verified, and the pinching-type SiGrad (P-Sigrad) is newly proposed to improve the estimation accuracy of SiGrad.