Masatsugu Takemoto

Improved analysis of a bearingless switched reluctance motor

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. Bearingless switched reluctance motors have combined characteristics of switched reluctance motors and magnetic bearings. Production of radial force for rotor shaft magnetic suspension is explained with differential stator windings. Mathematical relations between motor currents and radial force are derived by considering cross coupling and fringing fluxes. Theoretical relationships are verified with experimental results at partial overlap positions.

Radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. These motors are characterized by integration of switched reluctance motors and magnetic bearings. It is essential for a control system to consider magnetic saturation in real time in order to realize stable operation at a full torque load. Thus, this paper proposes a method for fast calculation of radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation. It is shown experimentally that the proposed method is effective in calculating the radial force and the torque under conditions of magnetic saturation.

A method of determining the advanced angle of square-wave currents in a bearingless switched reluctance motor

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. Bearingless switched reluctance motors have combined characteristics of switched reluctance motors and magnetic bearings. In this paper, a method of determining advanced angle of square-wave currents in bearingless switched reluctance motors is proposed. Under every torque condition from no load to full load, the stable operation is realized by opportunely determining the advanced angle of square-wave currents with the proposed method. It is shown in experimental results that the proposed method is effective for stable operation.

A new control method of bearingless switched reluctance motors using square-wave currents

Bearingless switched reluctance motors have the combined characteristics of synchronous motors and magnetic bearings. Radial force production for rotor shaft magnetic suspension is explained with differential stator windings composed of the motor main windings and radial force windings. In this paper, a new control method with square-wave currents in the motor main windings is proposed. Under every condition, from no load to full load, stable operation is realized by opportunely controlling the advanced current phase angle /spl theta//sub m/, and the current pulse width /spl theta//sub m/ with the new control method. The rotational torque produced by the radial force winding currents is also considered in the new control method. It is shown in experimental results that a proposed method is very effective for stable operation at no load.

A deeply-buried permanent magnet bearingless motor with 2-pole motor windings and 4-pole suspension windings

-Various permanent magnet bearingless motors, which can control rotor radial positions with magnetic force actively, have been proposed and developed. These bearingless motors are characterized by integration of permanent magnet motors and magnetic bearings. However, these bearingless motors cannot generate suspension force effectively, because suspension flux necessary for generating the suspension force passes through permanent magnets which have large magnetic reluctance. Accordingly, this paper proposes a novel deeply-buried permanent magnet bearingless motor with 2-pole motor windings and 4-pole suspension windings. In the proposed motor, the suspension flux does not pass through the permanent magnets. Thus, the proposed motor is shown to generate suspension force effectively. In addition, a control method of the proposed motor and its drive system are theoretically analyzed, and it is shown experimentally that the proposed drive system is effective in realizing stable operation of magnetic suspension. Keywords--permanent magnet motors, magnetic bearings, bearingless motors, magnetic suspension.