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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]

Interior permanent magnet synchronous motors (IPMSMs) are often used in applications that demand high performance. Interest has increased in designing IPMSMs in the enlargement high-efficiency operation area. Designing to meet such specifications can be difficult and time consuming. Combining a genetic algorithm (GA) with the coarse mesh finite element method (FEM) can automate the process and reduce the time it takes to design an IPMSM to meet such specifications. This study describes the motor design and explores the usefulness of designing motors having the large high-efficiency operation area using the GA combined with the coarse-mesh FEM. [ABSTRACT FROM AUTHOR]

Although motors that use rare-earth permanent magnets typically exhibit high performance, their cost is high, and there are concerns about the stability of the raw material supply. This paper proposes a permanent-magnet-assisted synchronous reluctance motor (PMASynRM) with a ferrite magnet that does not use rare-earth materials considering productivity. The performance of the proposed PMASynRM is evaluated based on the finite-element method and an experiment using a prototype machine. The analysis results reveal that the proposed PMASynRM has the same power density and an equivalent efficiency as rare-earth permanent-magnet synchronous motors for hybrid electric vehicles (2003 Toyota Prius). Furthermore, some experimental results are presented in order to validate the analytical results. As a result, the proposed PMASynRM was found to achieve high-power-density and high-efficiency performance. [ABSTRACT FROM AUTHOR]

Although motors that use rare-earth permanent magnets (PMs) typically exhibit high performance, high costs and concerns about the stability of raw material supplies are leading to their decreased production. However, the performance of such motors is not easily matched without the use of rare-earth PMs. This paper proposes and examines a PM-assisted synchronous reluctance motor with ferrite magnets that has the same power density as rare-earth PM synchronous motors. A suitable rotor structure for high torque and high power is discussed with respect to the demagnetization of ferrite magnets and the mechanical strength. [ABSTRACT FROM PUBLISHER]

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]

The importance of reducing the amount of rare earth materials used in high-performance permanent magnets has been established. However, the performance of such motors will not be easy to match without the use of rare earth materials. Although the torque characteristic of the motor can be improved by shortening the air gap length of the motor, there is a mechanical limitation on the gap length. In this paper, a 3-D air gap structure of the motor is proposed to improve the torque characteristics without shortening the gap length. The 3-D air gap structure is demonstrated to be equivalent to shortening the actual gap length to approximately 70% of the original length. Some disadvantages in the 3-D air gap structure are also described. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel control scheme for maximum power operation of synchronous reluctance motors. The proposed scheme consists of a combination of maximum torque per ampere control, maximum torque per flux control, flux-weakening control, and torque limiting. The first three control methods are based on a mathematical model in a rotating reference frame that is synchronized with the stator flux linkage. The final method utilizes a reactive torque calculated as the inner product of the flux and current vectors. The proposed control scheme is suitable for direct torque control (DTC) or flux-oriented control. In this paper, the scheme is applied to a DTC-based motor-drive system. The validity of the control scheme is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

The influence of rotor configuration on sensorless control for interior permanent-magnet synchronous motors (IPMSM) with concentrated windings is evaluated. Sensorless control that gives estimated angle with simple integration procedure and the biased convergent point observer is applied. Two types of rotors are analyzed and their robustness for an offset value of the observer is compared. To analyze the influence of magnetic saturation, nonlinear motor voltage equation is solved. Finite-element analysis plays an important role to realize high-speed and precise analysis. Analyzed results show that the rotor which has salient poles on the side of permanent magnets is insensitive to the offset value of the observer. And the sensitivity to the offset value of the observer with these two types of rotors is confirmed by experimental results. [ABSTRACT FROM AUTHOR]

A synchronous reluctance motor has many advantages because it has no permanent magnet, such as low back emf in high-speed operation, maintaining performance in a high-temperature environment, and so on. Therefore, many rotor constructions have been studied and developed. The rotor with multiflux barrier structure has the merit of easy construction and high performance. The linear synchronous reluctance motor has been developed. It is necessary to improve the performance of the mover design for industrial use, because of its low power factor. In this paper, we propose a novel configuration of mover for the linear synchronous reluctance motor, and examine the static characteristics of the motor with reluctance equalization design by means of the finite element method. From analytical results, it is demonstrated that the static characteristics of the linear synchronous reluctance motor are greatly improved by the reluctance equalization design at the iron layer in the mover. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 61–69, 2002; DOI 10.1002/eej.1139 [ABSTRACT FROM AUTHOR]