Alnico Permanent Magnet Generator Pole Shape Evaluation using Finite Element Analysis

Complex demagnetization characteristics of Alnico permanent magnet material forces pole design procedure to rely upon empirical methods. The Alnico material adopts several B-H (flux density-coercive force) curves due to nonhomogenous demagnetization, thereby causing hand calculations for magnet working conditions and generator voltage to be nebulous. A method is presented which yields the magnetic operating characteristics of the Alnico pole and corresponding generator terminal voltage for a given load current. The finite element modeling of the pole is based on a field solution of the magnet's severest previous demagnetization.