Bearingless Flux-switching Motor Research Articles

Fault-Tolerant Operation Control Strategy for Combined Winding Bearingless Flux-Switching Permanent Magnet Motor Drive System With One Opened Phase

The failure of the inverter bridge arm or the open circuit of the phase winding may occur during the operation of a combined winding bearingless flux-switching motor, causing both rotor rotation and suspension to malfunction, hence fault-tolerant control is vital for the motor's reliability and stability. In this paper, a fault-tolerant operation control strategy for combined winding bearingless flux-switching permanent magnet motors under open-circuit fault condition is proposed. Firstly, how to control the electromagnetic torque and suspension force acting on the rotor with the combined winding structure is explained, and then the mathematical models of the torque and suspension force which can be controlled individually by different current components are deduced in detail. Afterward, the relation of the phase current without and with winding fault is discussed, and the operation conditions of maintaining constant torque and suspension force after fault are demonstrated. Whereupon, the fault-tolerant control block diagram is constructed. Finally, the experimental results are presented to demonstrate the performance of the proposed strategy.

Topology Choice and Optimization of a Bearingless Flux-Switching Motor with a Combined Winding Set

The purpose of this paper is to choose a new topology for bearingless flux-switching slice motors, regarding the number of stator and rotor poles, with a combined winding set. Additionally, the selected motor topology is optimized with finite element method (FEM) simulations to improve the performance. Bearingless slice drives feature a magnetically-suspended rotor disk passively stabilized by reluctance forces due to a permanent magnet (PM) bias flux in the air gap and actively controlled by the generation of radial bearing forces and motor torque. Usage of the combined winding set, where each phase generates both motor torque and suspension forces, opens the opportunity for a new topology. The topology choice and optimization are based on FEM simulations of several motor optimization criteria, as the passive axial, tilting and radial stiffness values and the active torque and bearing forces, which are simulated regarding the motor height and specific stator and rotor parameters. Saturation, cogging torque and cogging forces are also analyzed. The 3D FEM program ANSYS Maxwell 2015 was used. The results led to an optimized bearingless flux-switching motor topology with six new stator segments and seven rotor poles. By optimizing the geometry, a considerable improvement of performance was reached. This geometry optimization is a base for a future prototype model.

Magnetic Levitation Systems for Cost-Sensitive Applications—Some Design Aspects

Alongside technical performance features, low system costs are the highest priority in the field of low-power electric drives. This makes adoption of magnetic bearing technologies difficult in applications with higher production volumes. Since published literature on cost-saving measures in this field is scarce, we present in this paper some ideas and stimuli using three selected examples: 1) a highly integrated hybrid bearing that provides active stabilization in 3 degrees of freedom (DOF); 2) a brushless permanent magnet motor with additional axial bearing capability; and 3) a bearingless flux-switching motor. We describe their particular designs and operational features, and compare the additional mechanical and electrical costs of these and similar systems with those of standard motor technologies. This paper concludes with a stability analysis of example 2), since it features passive permanent magnetic bearings, which are inherently only weakly attenuated.