Partial Demagnetization of Permanent Magnets in Electrical Machines Caused by an Inclined Field

We report a study of partial demagnetization of axially pressed sintered Nd-Fe-B magnets by inclined pulse demagnetization measurements, including a recoil behavior of the Nd-Fe-B material. From these measurements, we develop a simple empirical model for demagnetization of Nd-Fe-B magnets caused by an inclined field. We calculate demagnetization of a simple surface-magnet machine and a two-pole high-speed machine by using an exponent function-based model, taking also the inclined demagnetizing field into account. We show that it is not enough to consider only antiparallel demagnetizing field components in accurate demagnetization calculations.