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Bearingless switched reluctance motor (BSRM) adopts a doubly salient structure without windings on the rotor. BSRMs have the advantages of high rate of fault tolerance and simple structure, high power, super high speed and strong adaptability. They have broad application prospects in aerospace, flywheel energy storage, new energy and biomedical fields. Firstly, the suspension operation mechanism of a conventional double winding BSRM is described in this paper. The coupling between torque and suspension force is analyzed with a finite element method. On this basis, from the perspective of magnetic circuit optimization of the torque system and suspension system, the magnetic circuit design, decoupling mechanism and performance characteristics of self-decoupled BSRMs with different topological structures are described centering on the self-decoupled topology form of the BSRM. Finally, the study and development of BSRMs in the future are prospected based on the research status.

Abstract The current research of supporting and transmission system in flywheel energy storage system (FESS) focuses on the low consumption design. However, friction loss is a non-negligible factor in the high-speed but lightweight FESS energy and momentum storage with mechanical-type supporting system. In order to realize the support system without mechanical loss and to maximize the efficiency of the flywheel battery, a permanent magnet biased magnetic bearings (PMBMB) is applied to the FESS with the advantages of low loss, high critical speed, flexible controllability and compact structure. In this frame, the relevant research of three degrees of freedom (3-DOF) PMBMB for a new type FESS is carried out around the working principle, structural composition, coupling characteristics analysis, mathematical model, and structural design. In order to verify the performance of the 3-DOF PMBMB, the radial force mathematical model and the coupling determination equations of radial two DOF are calculated according to an equivalent magnetic circuit, and radial–axial coupling is analyzed through finite element analysis. Moreover, a control system is presented to solve the control problems in practical applications. The rotor returns to the balanced position in 0.05 s and maintains stable suspension. The displacement fluctuation is approximately 40 μm in the y direction and 30 μm in the x direction. Test results indicate that the dynamic rotor of the proposed flywheel energy storage system with PMBMB has excellent characteristics, such as good start-of-suspension performance and stable suspension characteristics. The proposed research provides the instruction to design and control a low loss support system for FESS.

In this paper, the electromagnetic vibration characteristics of hybrid excitation doublestator Bearingless Switched Reluctance Motor (HEDSBSRM) used in flywheel battery are analyzed when the rotor is eccentric. Firstly, the influence of rotor eccentricity on motor vibration is theoretically analyzed. Then the finite element method is adopted to study the radial electromagnetic force of the motor in the two-dimensional air-gap region. In addition, the three-dimensional equivalent vibration model of the motor outer stator is established, and the mode shapes and natural frequencies of the motor stator are obtained by the modal analysis. The vibration characteristics of the outer stator under eccentric motion are analyzed by the coupling calculation of electromagnetic field and mechanical field. Finally, the modal combination principle is used to analyze the vibration characteristics of the motor running at multiple speeds under eccentric condition. The results show that the vibration of HEDSBSRM is closely related to eccentricity, which affects the motor performance and lays the foundation for the optimization design of HEDSBSRM application in flywheel battery. [ABSTRACT FROM AUTHOR]

In this paper, a built-in hybrid magnetic bearing (BHMB) with a permanent magnet (PM) motor is proposed to reduce the axial length of the system. The BHMB shares the same distributed hollow rotor with an external PM motor. The structure and principle of BHMB are illustrated. The mathematic model of BHMB is deduced to design parameters, and the influences of parameters are analyzed. To improve the performance indexes of BHMB, a multi-objective optimization method based on Taguchi method is proposed. The values of parameters of BHMB can be chosen according to the proportion of each parameter. Finally, the finite element analysis (FEA) and experiment are used to verify the correctness of BHMB. [ABSTRACT FROM AUTHOR]

Bearingless switched reluctance motor can be used in aerospace and flywheel energy storage industry. Taking a 6/4/4 hybrid excitation double stator bearingless switched reluctance motor as an example, the motor adopts an E-block structure on the outer stator and is excited by permanent magnet and current. The loss calculation and thermal analysis of the motor is carried out by using finite element method. The result shows temperature distributions of the motor under natural air-cooling condition. The temperature change under different operating status is analyzed. Finally, the temperature change and transient temperature curve of each part of the motor are obtained through simulation, and the motor can run stably. [ABSTRACT FROM AUTHOR]

In order to research the temperature distribution of a hybrid excitation double stator bearingless switched reluctance motor (HEDSBSRM), the finite element method (FEM) is used to conduct thermal modeling and analysis. First, 2D FEM is used to calculate the losses of the motor, including the core losses and copper losses of the windings. Then, in the thermal analysis module of ANSYS Workbench software, losses are used for calculation and analysis as the thermal load. Furthermore, in order to enhance the accuracy of modeling, this paper also considers the equivalent thermal conductivity of each part of the motor, and the equivalent insulation of the windings and surface convection heat transfer coefficient are also considered. Finally, the simulation results of motor temperature field distribution are analyzed and studied in detail. The thermal characteristic is also of guiding significance to the optimal design of the motor. [ABSTRACT FROM AUTHOR]

In order to solve the strong coupling problem of a traditional bearingless switched reluctance motor (BSRM), this paper proposes a new type of hybrid excitation double stator BSRM (HEDSBSRM). The new motor can realize self-decoupling between torque and suspension force. In addition, the two degrees of freedom suspension force can also be decoupled. First, the topology of the motor is proposed, and the generation mechanism of suspension force and torque are expounded. Second, the torque winding structure is optimized. The multi-objective sensitivity optimization design method is used to screen out the key structural parameters that have the greatest influence on the average suspension force, average torque, and core loss. Then, the optimal structural parameters are obtained by the control variable method. Finally, based on the optimized motor, the finite element method (FEM) is used to analyze the electromagnetic characteristics including the suspension force, torque, and coupling of the motor. The simulation results verify the correctness of the proposed design method and analysis of motor performance. [ABSTRACT FROM AUTHOR]

To achieve radial suspension and eliminate the effect of rotor gravity in wind turbines, a novel structure of a generator combined with a magnetic bearing (GCWMB) is proposed in this paper. The GCWMB not only has the characteristics of the traditional permanent magnet (PM) generator but also has the advantages of reducing friction and starting wind speed, eliminating rotor gravity. The structure and principle of the GCWMB are analyzed in this paper. To improve the calculation accuracy of flux density, an analytical model based on the Fourier series decomposition is proposed to establish the model of flux density in the outer air gap. Taking into account the edge effects and the eccentricity of the rotor, an improved equivalent magnetic circuit method is adopted to model and analyze the flux density in the inner air gap. The effectiveness and correctness of the proposed analytical model in the outer and inner air gaps are verified by finite element analysis (FEA) and experiments. [ABSTRACT FROM AUTHOR]

A hybrid double stator bearingless switched reluctance motor with advantages of high suspension output, small loss and weak coupling is presented. This motor can realise electric/power generation and radial two-degree-of-freedom suspension. The biased magnetic field for producing radial force is provided by a permanent magnet, which reduces system power consumption. Self-decoupling is realised between a torque system and suspension system according to the mechanical structure design. Furthermore, the radial force is approximately constant when the suspension current is constant, thereby improving the controllability of the system. The operation principle is introduced and the electromagnetic characteristics are analysed through the timestepping finite element method. This analysis verifies the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]