Fundamental Study On Sharing Suspension Windings Bearingless Switched Reluctance Motor

The Bearingless Switched Reluctance Motor (BSRM) integrates both advantages of magnetic bearings and switched reluctance motor, where the suspension windings share the same stator core as the original stator torque windings, and a suitable control strategy is used to adjust the currents in both windings in such a way that the resultant radial forces support the rotor suspending in the stators center and the produced torque drives the rotor. However, the conventional double-winding BSRM has many suspension windings, e.g. three-phase motor features6sets of suspension windings. And the suspension windings have to be switched frequently during the torque windings commutation. As a result, the power converter requires many switches, and the control method and its implementation are complex, which increases the system cost and failure rate.Sharing suspension windings BSRM is proposed in the dissertation. The proposed BSRM uses only two suspension windings independent of the phase number to implement the rotor radial suspending. Because the number of suspension windings is greatly reduced, the motor structure becomes simpler. During motor operating, there is no need to switch the suspension windings. The number of IGBTs used in the power converter is reduced a lot, when compared to those required in the double-winding BSRM. The control circuit and algorithm have both been significantly simplified. The key foundation problems of the sharing suspension windings BSRM are studied in this dissertation.Firstly, the electromagnetic field of the sharing suspension windings BSRM are calculated in detail based on the Finite-element (FE) calculation. The suspension capacity and the affection of suspension windings on static torque are analyzed. The suspending force and the torque characteristics were obtained for different rotor positions and winding currents. The magnetic suspension performances of the sharing suspension windings BSRM and the double-winding BSRM are compared. The results indicate the proposed BSRM have a good suspension and rotation performance. The saturation effect on the suspending force and the torque has been also studied. The suspension controllability is verified even though the magnetic saturation of the sharing suspension windings BSRM.The magnetic equivalent circuit method is employed to obtain the self-inductances and mutual-inductances of the motor main windings and suspension windings. The affection of rotor eccentricity on the air-gap permeances between the stator and rotor tooth poles is accurately analyzed. The mathematical relationship among the rotor radial eccentricity, the air-gap length between the stator and rotor tooth poles and the mechanical position of stator is derived. The straight flux paths are combined with the elliptical fringing flux paths to calculate the air-gap permeances.Based on the calculated air-gap permeances the windings inductances of the motor and the stored magnetic energy are obtained when the rotor is located at the central point of the stator. Then, the mathematical expressions of radial forces and torque are derived. A sharing suspension windings BSRM prototype is analyzed through using the proposed analytical model and the finite element model (FEM). The proposed mathematical model of the sharing suspension windings BSRM is verified by Finite-element analysis results.Analytic modeling of radial forces is proposed for the sharing suspension windings BSRM, where the affection of rotor eccentricity on the air-gap permeances between the stator and rotor tooth poles is taken into account. The radial force model describing the relationship between the radial force, winding currents, rotor position angle, and rotor eccentricity displacement is derived. The FEM results verify the proposed radial force model.The control scheme based on inverse-system method was proposed for the serious non-linearization system of the sharing suspension windings BSRM radial suspension force. A synthesize control scheme of easily regulating control parameters according to dynamic performance remands was designed. Dynamic linearization control of radial force was achieved. The rotor radial position simulations results which satisfy the different dynamic performance remands verify the proposed method.Finally, the experimental platform of the sharing suspension windings BSRM is built to finish the preliminary static suspension and rotation suspension experiments. The systemic study results show the suspension controllability and excellent performance. The dissertation provides the basis for further research of the sharing suspension windings BSRM.