To address the challenge of low torque density of conventional switched reluctance motor (SRM), this article introduces a modular stator hybrid-excitation SRM (MS-HESRM) with a π-type structure. Permanent magnets (PMs) are magnetized in circumferential direction and placed in stator yoke between the adjacent π-type modules, which enhances the flux flowing through the torque poles and thus improves the output torque. First, the operation principle of proposed structure is explained. And the magnetic circuit model is analyzed to reveal the torque contribution of PMs. Furthermore, the influence of structural parameters on the output performances such as average torque, torque/PM volume, and cogging torque, are investigated using finite-element method. To demonstrate the merits of proposed structure, a prototype is manufactured, and comparisons with other hybrid-excitation SRMs are implemented including average torque, torque/PM volume etc. Simulation and experimental results illustrate that the proposed MS-HESRM has high output torque, PM utilization and torque density.

This article presents a robust adaptive direct torque control (DTC) strategy to reduce torque ripple for switched reluctance motor (SRM). To realize high-precision torque control and take the high nonlinearity of torque variation with rotor position and current into account, a total torque dynamics model containing two nonlinear functions is established. Furthermore, an adaptive torque controller is proposed which realizes the estimation of nonlinear functions using the designed adaptive laws, and its stability is proved based on the Lyapunov function. In the meanwhile, the convergence of the adaptive parameters toward their optimal values is analyzed, and the selection rules of the design parameters are given. In addition, the mechanism for compensating the controller gain by the adaptive operator is discussed in detail. Finally, experiments are carried out on 3-phase SRM to verify the adaptive capability of control parameters, robustness to motor model uncertainty, and torque ripple reduction effect of the proposed DTC strategy.

This article proposes a regional sliding mode observer for position estimation and sensorless control of switched reluctance motors (SRMs). This method utilizes incremental inductance, obtained through high-frequency pulse injection in the idle phase, as a mapping of the true rotor position. In the meanwhile, a regional error function is designed by comparing the incremental inductance with the observed inductance, and this error within the inductance decreasing region is used as input for a sliding mode observer. Furthermore, stability analysis is conducted to demonstrate convergence of position error. To validate the effectiveness of this approach, experiments are implemented on a three-phase 12/8 SRM prototype. Experimental results indicate that the observer exhibits strong stability and robustness. It can still achieve position estimation even in the presence of significant incremental inductance errors. Additionally, position observation can be accomplished well in the face of phase faults.

In order to address the challenges of high loss density, difficult heat dissipation, and irreversible demagnetization in high temperature of high-speed permanent magnet machine, an innovative cooling structure with axial ventilation and self-cooling rotor is proposed to enhance temperature distribution. The cooling efficiency of the cooling structure is defined, and the influence of the rotor vent on the electromagnetic and air friction loss is analyzed. The governing equation for the fluid flow in a rotating pipe is derived from a fluid model analysis of a ventilation hole rotating at any angle to the axis of rotation. The calculated results are validated against the results obtained from computational fluid dynamics. The sensitivity of rotor cooling performance to various control factors using the variance index method. Subsequently, the cooling structure was enhanced based on the findings of the analysis. The calculation results indicate that the heat dissipation effect of the axial ventilation self-cooled rotor has decreased by 4.17 °C compared to before the improvement. The temperature rise experiment verified the accuracy of temperature calculation and the effectiveness of the cooling structure, providing strong support for the design of axial self-ventilation cooling system for high-speed machines.

High-speed permanent magnet synchronous machines (HSPMSMs) are widely utilized in a variety of industrial applications, such as aerospace and flywheels. The key technical problems, that is, the development of HSPMSMs to high power and high speed, are temperature rise and stress concentration of the rotor. In order to solve the key technical problems, novel composite magnetic materials are proposed in this article. Novel composite magnetic materials are composed of magnetic powder, epoxy, and carbon fiber. In this article, the preparation and molding process of novel composite magnetic materials are proposed. Considering the thermal expansion of epoxy, the analytical model on magnetic properties of novel composite magnetic materials is established. The simulation model of novel composite magnetic materials is determined, and the magnetic properties of magnetic materials with the variation of parameters are analyzed. And the rotor stress and eddy current loss of HSPMSMs are analyzed by the finite-element method (FEM). Finally, the accuracy of the analytical model is verified by the experimental results. The theoretical foundation for the popularization and application of novel composite magnetic materials in HSPMSMs is laid.

Rotor strength issues are the main problem limiting the development of high-speed permanent magnet motors (HSPMMs) towards higher operating speeds. The permanent magnet part of the traditional high-speed permanent magnet motor adopts sintered NdFeB, and its tensile strength limit is 80MPa. Therefore, this paper proposes a composite rotor on the HSPMM for regional aircraft system, which uses a higher strength composite magnetic material instead of sintered NdFeB to improve the rotor strength. In order to study the influence of composite magnetic materials on the rotor strength, a multi-scale method of numerical analysis is proposed in this paper. The micro-to-macro model is used to study the relationship between the composite material mixing ratio and the rotor strength. The results of the obtained simulation data are verified by experiments and have good consistency. It provides a theoretical basis for the design of high-strength motor rotor using composite materials.