The switched reluctance motor (SRM) benefits from its magnet-free nature, robust construction, low cost, flexible controls, and the ability to operate in harsh environments such as high temperatures and high pressure. It has received increasing attention for all-electric or multi-electric aircraft systems and electric vehicles (EVs) as compared with permanent magnet synchronous motors (PMSM) and other AC motors in some required high reliability and fault tolerance applications. However, the SRM is prone to considerable wind resistance due to the convex pole structure of the rotor during high-speed rotation, high torque ripple, and also vibration noise. Thus, it is currently a trending topic to develop special SRMs, tailored with high reliability and fault tolerance. Recent research demonstrates several promising feasible solutions to reduce torque ripples and enhance torque density and power factors, including changing topology of SRM, using advanced control methods, as well as different winding configurations. Among these options, the segmented switched reluctance motor (SSRM), as a deformation of the conventional topology, is shown to be capable of effectively optimizing the torque performance. Motivated by this advance, this paper aims to present a comprehensive literature review on the SSRM, first illustrating the development of the topology of the SRM, then providing a description as well as a classification according to the topology of the SSRM. In particular, we focus on the evolution of various kinds of segmental topology and improvement measures. Then, we discuss the performance, advantages, and disadvantages of various types of structures in terms of their electromagnetic aspects and their applications. Eventually, several promising future trends and application prospects of the SSRM are prospected, with the aim of shedding light on further research. In sum, the key contribution of this paper is to provide a valuable basis for detailed analyses of the structure and electromagnetic design of the SSRM that are expected to benefit future research.

Low-power and high-speed BLDC(Brushless DC) motor is widely used in vacuum cleaners. This paper presents a sensorless speed control scheme for a high-speed BLDC motor of a hand-stick vacuum cleaner using a variable slope sliding mode observer(SMO). The SMO using the signum function is very effective for the sensorless estimation of the BLDC motor. However, the chattering effect on the slide surface from the signum function decreases the sensorless performance in the wide speed range. The sigmoid function instead of the signum function can reduce the chattering effect. However, the convergence is inversely proportional to the reduced chattering effect. In order to reduce the chattering effect and keep the proper convergence performance, the proposed method uses a variable acceleration slope of the sigmoid function. In the low-speed range, the acceleration slope of SMO is decreased to reduce the chattering. And, it is increased to improve the convergence in the high-speed region. The acceleration slope of the sigmoid function is designed as a function of the estimated speed to keep the constant convergence with reduced chattering in the sensorless speed and position estimation. In order to verify the proposed sensorless control scheme, 115 krpm speed 540W BLDC motor for a vacuum cleaner is tested with various SMO methods. In the experimental results, the proposed method shows better sensorless speed control performance in the wide speed range.

This paper focuses on a minimal current sensing strategy and fault detection of Switched Reluctance Machines (SRMs). In order to reduce the number of required current sensors in multiphase motor drives, the optimal selection and location of current sensors is presented in consideration of the precise actual phase current measurement, open- and short-circuit fault detection. The proposed scheme requires two current sensors to replace the phase current sensors placed in each phase without any additional devices for multiphase SRMs to achieve a more compact and low-cost drive. Different current regulation methods are employed for single phase conducting region and commutation region. To obtain the phase currents from the proposed approach, different settings of the pulse-width modulation (PWM) signals for adjacent phases during the commutation region are implemented. The simulation and experiments on a four-phase 8/6 pole SRM are carried out to verify the effectiveness of this approach in the healthy and faulty cases.

This paper proposes a novel 12/8 switched reluctance motor (SRM) with segmental rotor for vehicle cooling fan application. Unlike conventional SRMs, the proposed motor adopts one body stator with hybrid stator poles and segmental rotor structures, thereby making the motor operate in short flux paths and parts of the flux paths magnetically isolated between the phases. Therefore, compared with conventional SRMs, the proposed structure not only improves the output torque density and reduces the magneto-motive force (MMF) requirement and core losses of the motor, but also inherits the advantages of conventional SRMs like flexible control as well as the adaptability in harsh environments. To verify the proposed structure, finite element method (FEM) is employed to get characteristics of the proposed SRM. Meanwhile, a conventional 12/8 SRM which has been used for vehicle cooling fan application is also analyzed for comparison. Furthermore, the prototypes for the conventional and proposed 12/8 SRMs are manufactured and tested. Finally, the simulation and experimental results are presented and analyzed to verify the effectiveness of the proposed SRM.