High speed motors that develop rotational speeds in excess of 5000 rpm are necessary for centrifugal and screw compressors, grinding machines, mixers, pumps, machine tools, textile machines, drills, handpieces, aerospace, flywheel energy storages, etc. The actual trend in high speed electromechanical drives technology is to use PM brushless motors, solid rotor induction motors or switched reluctance motors. The highest efficiency and highest power density is achieved with PM brushless motors.