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Synchronous reluctance motors (SynRMs) with four layers of flux barriers are currently in practical use as high-efficiency motors for industrial applications. While SynRMs have higher efficiency than induction motors, they have a high torque ripple. In this study, an asymmetric rotor structure was designed to reduce the torque ripple of the four-layer SynRM, considering the mechanical strength. Two rotor structures with different flux barrier angles were combined in the stacking direction, and the ratio of the combination was optimized by finite element analysis. In addition, prototypes of the initial structure and proposed asymmetric structure were manufactured, and their torque and efficiency characteristics were measured. The experimental results show that the proposed asymmetric structure can reduce the torque ripple while maintaining the basic characteristics such as average torque and efficiency. [ABSTRACT FROM AUTHOR]

When direct torque control (DTC) is applied to permanent-magnet synchronous motor (PMSM) drives, the relationship between the torque and stator flux linkage is important for high-efficiency drives because DTC requires them as references. In the stator flux linkage synchronous frame (M–T frame), the torque is described by a simple equation using the T-axis current. However, the M-axis current is neglected in the equation. This paper derives the relationship between the M-axis current and the stator flux linkage, and proposes a maximum torque per ampere (MTPA) control strategy for direct torque controlled PMSM drives using the above relationship. The proposed method does not require the q-axis inductance, which often varies due to the magnetic saturation. The simulation and experimental results verify that the MTPA condition can be obtained with the proposed method. [ABSTRACT FROM AUTHOR]

In this study, we investigate the torque response of a control system that is based on the direct torque control (DTC) principle for an interior permanent magnet synchronous motor (IPMSM). We also propose a gain-scheduling method for improving the torque response. Reference flux vector calculation (RFVC) DTC is used in this study. In RFVC DTC, a PI controller is used for torque control; this is in contrast to the use of the hysteresis comparator and switching table in basic DTC. In this paper, we present the relationship between the torque response and the gain of the PI controller. This relationship is derived by using the transfer function of the torque control loop. We also examine the difference between the torque responses of two motors that have different machine parameters. The proposed method can be used to realize a torque response that is independent of the operating torque. The simulation results and experimental results presented in this paper show the validity of the derived relationship as well as the effectiveness of the proposed method. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(2): 55-65, 2012; Published online in Wiley Online Library (). DOI 10.1002/eej.21198 [ABSTRACT FROM AUTHOR]

This paper proposes a control method suitable for limited armature voltage and current in a permanent-magnet synchronous motor drive system based on direct torque control (DTC). First, this paper proposes torque-limiting and flux-weakening controls that are suitable for a DTC-based motor drive system. The proposed method utilizes a mathematical model in a rotating reference frame synchronized to the stator flux linkage. Second, this paper proposes an antiwindup scheme for the torque controller of the DTC system. Windup of the controller degrades the performances of torque-limiting (current-limiting) control and of torque control. Applying the antiwindup results improves the performance of the proposed torque-limiting method in the transient state. This paper presents a DTC-based drive system combined with a speed controller. The proposed system can achieve stable control, and its effectiveness is confirmed experimentally. [ABSTRACT FROM PUBLISHER]

This paper describes an approach in improving the performance of the position sensorless control of an interior permanent-magnet synchronous motor using parameter identification. The model-based sensorless method requires accurate motor parameters. At low speed, the resistance variation degrades the accuracy of position estimation. The identified parameter is used in the sensorless drive system to improve the accuracy of position estimation. In this paper, the resistance is identified online, but the offline identified value of the q-axis inductance is used. The experimental results reveal the effectiveness of applying parameter identification to the sensorless drive system. [ABSTRACT FROM PUBLISHER]

A sensorless-control technique for improving the performance of interior permanent-magnet synchronous-motor control such as the operating speed range and position estimation accuracy is proposed herein. The method presented is based on the estimation of an extended electromotive force in a rotating reference frame. The difference between the reference voltage and the actual voltage of the inverter is modeled and compensated for in order to improve the accuracy and the stability of the sensorless drive system. Moreover, an online parameter-identification technique is applied in order to improve the accuracy of position estimation. The effects of the proposed scheme are evaluated by the experimental results. [ABSTRACT FROM AUTHOR]