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Electric motors with a double air-gap structure offer increased power or torque density compared to their single air-gap counterparts, achievable through double-stator or double-rotor configurations. In a previous study, the authors proposed a double-stator permanent magnet synchronous motor (PMSM) with a magnetic screen placed in the middle of the rotor to isolate the outer and inner motors. However, the analysis of the magnetic screen was not provided in that study, as the design was arbitrarily chosen. This research focuses on the effects of the magnetic screen size and selects the appropriate dimensions for optimal motor performance. Finite element analysis (FEA) is employed to assess the electromagnetic characteristics of the screen. Subsequently, the motor is manufactured and tested. The results show that the chosen magnetic screen size contributes to significant efficiency improvements. In particular, the motor achieved an efficiency of 95.2% during the qualification test, surpassing the efficiency obtained in the previous study. [ABSTRACT FROM AUTHOR]

This paper introduces a novel dual-air-gap surface permanent magnet synchronous motor (DAG-SPMSM) and investigates its electromagnetic characteristics. The motor comprises two stators (inner and outer) and a single rotor with permanent magnets on both sides (inner and outer). The magnets are arranged in a zig-zag configuration to isolate the inner and outer stator and rotor magnets. Additionally, a magnetic shield is incorporated into the rotor to further isolate the rotor magnetic flux, which results in a localized short flux path that can reduce core loss. The insertion of the magnetic shield also affects the flux path, reducing torque ripple. The electromagnetic characteristics, such as flux path, flux density, and torque, are analyzed using finite element analysis. The effectiveness of using a magnetic screen is also evaluated, and simple experiments are conducted to validate the observed characteristics of the proposed motor. [ABSTRACT FROM AUTHOR]

With the rapid development of power electronic techniques and the increasing cost of permanent magnets (PMs) materials, switched reluctance motors (SRMs) have recently gained more attention. However, traditional SRMs have a relatively low torque density. For the sake of increasing the motor torque density, this paper proposes a novel segmental rotor type SRM. The proposed motor adopts hybrid stator poles and concentrated windings in the stator side and a segmental rotor structure in the rotor side, which is completely different from the structures of the traditional SRM. The special structure of the motor shortens the magnetic flux paths of the motor, separates the parts of the magnetic flux paths from one another, and eradicates the magnetic flux reversal in the motor stator in order to improve the electric utilization and output torque density of the motor. Meanwhile, the requirement of the magneto-motive force and the core loss of the motor is also decreased, thereby improving the efficiency of the motor. For the purpose of proving the proposed structure, the characteristics of the motor are analyzed using the finite element method and are compared to those of the traditional 12/8 SRM, which is designed for the same application. Moreover, the prototypes of the traditional 12/8 and proposed SRMs are manufactured, and experiments based on the prototypes are performed. Finally, the effectiveness of the structure of the proposed motor is further proven by the experimental results. [ABSTRACT FROM AUTHOR]

Servo motor drive systems with ball-screw and timing-belt are widely used in a numerical control, robot, factory automation and industrial applications. Most of the servo motor and drive system transfer the motor torque to loads via mechanical connections. However, the nonlinear friction of coupled mechanical devices reduces the performance of a servo drive. Especially, in a low speed range, tracking errors are serious due to the break-away friction and Stribeck effects. In this paper, a new dual speed controller is proposed for the compensation of nonlinear friction torque. The proposed dual speed controller has an outer speed controller and an inner friction torque compensator. The friction torque compensator adds additional torque corresponding to a nonlinear friction of mechanical devices, so the actual speed quickly tracks the reference value. Since the proposed nonlinear friction torque compensator uses the actual speed information without any motor parameters and mathematical model, the proposed compensator has a very simple structure and high stability. The proposed control scheme is verified by computer simulation and experimental results. Index Terms--Permanent magnet synchronous motor (PMSM).

In a single-phase switched reluctance motor (SRM) drive, the dc voltage source is generally supplied by a circuit consisting of a bridge rectifier and a filter capacitor connected to an ac line. The charging time of the capacitor is shorter from the ac source as capacity increases. The bridge rectifier draws pulsating current from the ac source, which results in a degraded power factor (PF) and lower system efficiency. A single-phase SRM drive system is presented in this paper, which includes the realization of a drive circuit for the reduction of torque ripple and PF improvement with a novel switching topology. The proposed drive circuit adds one switch and one diode, which can separate the output of the ac/dc rectifier from the large capacitor and supply power to the SRM alternately. This allows the drive system to realize torque ripple reduction and PF improvement through the switching scheme. The validity of the proposed method is analyzed by mathematical modeling and tested by simulations and experiments. Index Terms--Power factor correction (PFC), single-phase switched reluctance motor (SRM), torque ripple reduction.

A novel four-level converter and instantaneous switching angle detector for a high speed switched reluctance motor are proposed. Since the excitation time is very short compared to the general speed range of a high speed drive, the excitation current can not be built-up sufficiently. Also, the demagnetization current can be easily extended to the negative torque region. To obtain a fast current buildup and suitable demagnetization, a novel four-level converter is proposed. The proposed converter has an additional charge capacitor and an active power switch compared to a conventional asymmetric converter. The high voltage of the additional capacitor is applied to the phase winding in the fast excitation mode and the phase current is rapidly decreased during the recharging of capacitor in demagnetization mode. In addition, an instantaneous switching angle detector separated by main digital controller is designed for precise switching angle control. During high speed operation, rotor position error increases due to the constant sampling period of digital controller. The proposed instantaneous switching angle detector operates with optical encoder's pulse and pre-set switching position regardless of sampling time. So, it determines the precise switching pattern without time delay from sampling time. The proposed high speed control system is verified by computer simulation and experimental results. Index Terms--High speed drive, switched reluctance motor (SRM).

In a switched reluctance motor drive, it is important to synchronize the stator phase excitation with rotor position because the position of the rotor is an essential information. Although high-resolution optical encoders or resolvers are used to provide precise position information, these sensors are expensive. Moreover, in a high-speed region, switching angles are fluctuated back and forth out of the preset value, which is caused by the sampling period of the microprocessor. In this paper, a low-cost analog encoder suitable for practical applications is proposed. In addition, the control algorithm to generate switching signals using a simple digital logic is presented. The validity of the proposed analog encoder with a proper logic controller is verified from the experiments. Index Terms--Analog encoder, switched reluctance motor (SRM), switching angle control.