Eddy Current Analysis in Permanent Magnets Using the Variational Method

This article presents a new method for the calculation of eddy current losses in rectangular permanent magnets. Magnets with rectangular shapes are commonly used in interior permanent magnet (IPM) machines. The computation of eddy current losses in the permanent magnets is essential to avoid magnet heating and demagnetization. A variational method is utilized for the 3-D analysis of eddy current in the permanent magnets. A closed-form analytical formula is obtained for eddy current losses using the proposed variational method, which shows adequate accuracy. The finite dimensions of permanent magnet segments and the reaction fields of induced eddy current are considered in the calculations. The end effect factor for magnet conductivity correction for 2-D losses analysis is also calculated.