Memory motors-a new class of controllable flux PM machines for a true wide speed operation

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