Bearingless Switched Reluctance Motor Research Articles

Optimal Winding Arrangements of a Bearingless Switched Reluctance Motor

Winding arrangements of a bearingless switched reluctance motor strongly influence the operation state of its power converters so much as the rotation and levitation of the motor. This paper proposes some optimal winding arrangements, which suit for a three-phase half-bridge converter or a three-phase four-leg converter. First, the optimal main winding arrangement is proposed. Then, this paper analyzes the influence factors of the midpoint voltage of a three-phase half-bridge converter applied to the radial force winding under the invariable radial load. Consequently, four kinds of optimal winding arrangements are given, which can balance the midpoint voltage. Moreover, according to influences of the winding arrangement on the operation state of a three-phase four-leg converter applied to the radial force winding, the paper proposes other four kinds of optimal winding arrangements, which fit the three-phase four-leg converter. The experimental results are also included to verify the theoretic analysis.

Torque and suspension force in a bearingless switched reluctance motor

AbstractBearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. The bearingless switched reluctance motors are characterized by integration of switched reluctance motors and magnetic bearings. These motors have two kinds of stator windings composed of motor main windings and suspension windings in the same stator in order to produce suspension force that can realize rotor shaft suspension without mechanical contacts or lubrication. For successful stable operation, accurate theoretical formulas of instantaneous torque and suspension force are necessary to a rotational speed controller and a rotor radial position controller. This paper derives the theoretical formulas of the instantaneous torque and the suspension force from an assumption of simple permeance distribution. This derivation process makes an assumption that fringing fluxes are distributed on elliptical lines. It is shown with experimental results that the derived theoretical formulas are very accurate in terms of practical application. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(2): 72–82, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20157

Torque and Suspension Force in a Bearingless Switched Reluctance Motor

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. The bearingless switched reluctance motors are characterized by integration of switched reluctance motors and magnetic bearings. These motors have two kinds of stator windings composed of motor main windings and suspension windings in the same stator in order to produce suspension force that can realize rotor shaft suspension without mechanical contacts or lubrication. For successful stable operation, accurate theoretical formulas of instantaneous torque and suspension force are necessary to a rotational speed controller and a rotor radial position controller. This paper derives the theoretical formulas of the instantaneous torque and the suspension force from an assumption of simple permeance distribution. This derivation process makes an assumption that fringing fluxes are distributed on elliptical lines. It is shown with experimental results that the derived theoretical formulas are very accurate in terms of practical application. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(2): 72–82, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20157

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.

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.