CHARACTERISTICS OF A PERMANENT-MAGNET TYPE BEARINGLESS MOTOR

Super high-speed and high-power electric machines are required for tur bomolecular pumps and spindle drives. High rotational speed and high p ower drives can be achieved with bearingless motors. In this paper, a bearingless motor with principles of permanent magnet type synchronous motors is proposed. High power factor and high efficiency can be expe cted in permanent magnet type bearingless motors. The proposed bearing less motor is a 4-pole permanent magnet synchronous motor, in which ad ditional 2-pole windings are wound together with 4-pole motor windings in stator slots. With currents of 2-pole windings, radial magnetic fo rces are produced to support a rotor shaft. Principles of radial force production of surface-mounted permanent magnet bearingless motors are analyzed mathematically, It was found that radial forces are efficien tly produced by employing thin permanent magnets on the surface of rot or iron core. A test machine was built in order to measure inductance functions as well as relationships between voltages and currents.