Toru Shikayama

Drive characteristics of slotless PM motors

The rare-earth magnet whose BH-product is more than 30 MGOe makes the permanent magnet (PM) motor store attractive from a viewpoint of power density and efficiency. However, as the flux density becomes higher, the magnetic saturation in the stator teeth of the conventional slotted PM motor becomes severe. To overcome this problem, the slotless PM motor is expected to be one solution. In this paper, the basic design procedure of the slotless PM motor and the drive characteristics of the designed motor are presented. The designed motor has a rare-earth magnet on the rotor and the resin-molded helical windings are provided over the inner surface of the stator yoke. Since the inductance is small, the current is distorted, thus increasing the copper loss. The experimental studies of the effect of the current waveform on the performance are presented. By improving the current waveform, the designed slotless motor allows higher efficiency at higher speed.

Development of stator-magnetless linear synchronous motor for sensorless control

Sensorless control technique is desired in applications of a long stroke linear synchronous motor (LSM) without using a linear scale. This paper discusses the development of a stator-magnetless LSM (no magnet mounted on the stator of LSM) for sensorless control technique that includes a high speed position estimation algorithm based on magnetic hysteresis phenomenon. This paper presents the new structure of a flux-switching LSM to achieve a high saliency ratio by designing a cutout which causes magnetic saturation in the armature core. The effect of sub-teeth to reduce cogging thrust is also presented. Furthermore, this paper also reports the analytical and experimental characteristics of inductance, thrust, cogging thrust, and sensorless control drive using a prototype.

Experimental investigations into skin effect influences on current distortion and increase in loss for 20 kHz PWM-VSI-fed slotless PMSM drives

This paper presents the experimental investigations into skin effect influences on current distortion and increase in loss for 20 kHz PWM-VSI-fed slotless PMSM drives. At first, the relation between the current distortion and the skin effect of lamination steels caused by high frequency component of flux is examined. Secondly, the relation between the increase in loss and the skin effect of coils caused by high frequency component of current is investigated. Finally, the machine design aspects of reducing the current distortion and the associated losses are examined.

Development of a Stator-Magnetless Linear Synchronous Motor for Sensorless Control

Sensorless control technique is desired in applications of a long stroke linear synchronous motor (LSM) without using a linear scale. This paper discusses the development of a stator-magnetless LSM (no magnet mounted on the stator of LSM) for sensorless control technique that includes a high speed position estimation algorithm based on magnetic hysteresis phenomenon. This paper presents the new structure of a flux-switching LSM to achieve a high saliency ratio by designing a cutout which causes magnetic saturation in the armature core. The effect of sub-teeth to reduce cogging thrust is also presented. Furthermore, this paper also reports the analytical and experimental characteristics of inductance, thrust, cogging thrust, and sensorless control drive using a prototype.

Position sensorless control with accelerometer for linear and curvilinear synchronous motor

In the field of the manufacturing industry, it has been often discussed that high-mix low-volume manufacturing is required to meet a variety of customer needs. In such a situation, cellular manufacturing and U shaped production lines are often adopted. Linear synchronous motors (LSMs) are appropriate to realize U shaped automation lines because of its strong features such as flexibility of layout, high efficiency and position control performance. However, a problem seems to lie in the fact that LSMs need a position sensor which is expensive and has less durability. For this reason, the position sensorless control for LSMs is required. In addition, the method should be easy to apply to all kinds of LSMs. Specifically, the method should require no saliency and be apply to a LSM which has a complex track including curvilinear section. Based on such a background, this paper presents a position estimation method for a Linear and Curvilinear Synchronous Motor with an accelerometer which is inexpensive and easy to attach to LSMs. As the proposed method in this paper does not require any motor saliency, it can be quickly applied to all LSMs. In this paper, the proposed method is shown and verified by experimental results.