Abstract
A bearingless switched reluctance motor (BSRM) has the combined characteristics of a switched reluctance motor (SRM) and a magnetic bearing. The hybrid-rotor BSRM (HBSRM) discussed in the paper has a twelve-pole stator and an eight-pole hybrid rotor, which is composed of a cylindrical rotor and a salient-pole rotor. Although the asymmetry of the hybrid rotor makes the structure and magnetic field of the HBSRM more complex, it can always produce a significant amount of magnetic pulling force to levitate a rotor shaft at all the rotor angular positions of each phase, which is not available in a traditional BSRM. The classical mathematical model for a conventional BSRM is valid only when its rotor rotates from the start of the overlap position to the aligned position, and the radial force and torque derived from this model are discontinuous at the aligned positon, which is harmful to the motor’s stable operation. In this paper, a full-period mathematical model on the assumption that the gap permeance is cut apart by straight lines or improved elliptical lines for a 12/8-pole HBSRM is provided. On the basis of this mathematical model, the continuity of the radial force and torque at all the rotor angular positions can be guaranteed, and the fine characteristics of this mathematical model have been verified by simulations.
Highlights
Switched reluctance motor (SRM) has superior performance under special environments such as the starter/generator in all electric/multi-electric aeroengine, vacuum pump, and flywheel energy storage systems, because of its simple structure, low cost, robustness, and suitability for operation in high temperatures [1,2,3]
The SRM has a good feature as a bearingless motor, which is characterized by the integration of an electrical motor and magnetic bearing [4,5,6]
A bearingless switched reluctance motor (BSRM) with differential stator-winding configuration was proposed in References [7,8,9,10]
Summary
Switched reluctance motor (SRM) has superior performance under special environments such as the starter/generator in all electric/multi-electric aeroengine, vacuum pump, and flywheel energy storage systems, because of its simple structure, low cost, robustness, and suitability for operation in high temperatures [1,2,3]. Theoretical formulas of radial force and torque have been derived from a magnetic equivalent circuit of the 12/8-pole BSRM [7,8] In these models, the gap permeance has been cut apart by straight lines and elliptical lines for the BSRM. The specific reasons are as follows: The phase current cannot reach the given value quickly due to the bigger increase rate of inductance at the start of the overlap position between the stator and rotor poles, so the turn-on angle of each phase for a traditional SRM is usually set in the unaligned position or in the range of the inductance drop. The fine characteristics of this full-period mathematical model have been verified by simulations
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