Reduction of the external magnetic field (magnetic signature) of large electric motors may be important in military and other applications. This article deals with critical issues in the design and manufacturing of permanent magnet (PM) motors that are responsible for increased magnetic signatures. Emphasis is on analysis of the nonidealities of PM rotors such as imbalances in the permanent magnet excitation system due to manufacturing tolerances and differences in material properties. Spatial harmonic analysis is used to describe the magnetic signature. The rotor simulation considers rectangular PM segments, and uses statistical characterization of possible nonidealities in dimensions, positioning, and magnetization. The approach focuses on lower degree magnetic multipole moments (dipolar, quadrupolar, and octupolar) in spheroidal and spherical domains, and is applied to PM inducing elements.
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