High-speed DC motor or generator - has pole pieces on permanent magnets on internal frame to reduce demagnetising field

摘要

In the dc motor or generator demagnetising field in its inductive magnetics is reduced by interposing soft-iron pole pieces between the surface of the permanent magnets and the inducing parts. The thickness of the pole pieces is chosen to allow the flux to vary sufficiently without saturating the iron. The permanent magnets are fixed to the external face of an internal cylindrical soft-iron frame. The pole pieces are thicker at their centres than their sides thereby producing a variable-width gap with the external frame.