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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.

Permanent magnet materials are nowadays widely used in the electrical machine manufacturing industry. Eddy current loss models of permanent magnets used in electrical machines are frequently discussed in research papers. In magnetic steel materials we have, in addition to eddy current losses, hysteresis losses when AC or a rotating flux travels through the material.Should a similar phenomenon also be taken into account in calculating the losses of permanent magnets? Actually, every now and then authors seem to assume that some significant hysteresis losses are present in rotating machine PMs. This paper studies the mechanisms of possible hysteresis losses in PMs and their role in PMs when used in rotating electrical machines. Index Terms-Permanent magnet, permanent magnet material, permanent magnet losses, hysteresis, hysteresis in permanent magnets. I. INTRODUCTIONERMANENT magnet (PM) materials are widely used in electrical machines. The applications where permanent magnet machines are utilized include for example industrial machines, wind power generators, traction motors, linear machines, high-speed machinery, and machines used in aerospace applications [1]-[6].Eddy current loss models of PMs used in electrical machines are frequently discussed in research papers. Sintered PM materials have a significant macroscopic resistivity, in the range of 100-200 µΩcm, providing eddy currents with paths Manuscript