Memory Motors

A new class of permanent-magnet (PM) machines, named memory motors for their ability to change the intensity of magnetization and memorize the flux density level in rotor magnets is described in the article. A memory motor can be built either as a variable-flux or pole-changing machine. In both machine types, the magnetization of PMs can be simply varied by a short current pulse, with no need for permanent demagnetizing current as in conventional internal PM machines at flux-weakening mode. The demagnetizing current flows through stator winding(s) supplied from the same source as the stator current. Memory motors combine advantages of a wound-rotor machine (variable rotor flux) with those of a wide-speed machine (no excitation losses), resulting in a unique machine concept that has the potential to find numerous applications in electric drives.