This paper presents a method for reducing cogging thrust in permanent-magnet-type linear synchronous motors. A phase shift method and supplement tooth method are proposed. The methods do not affect the original thrust performance of the linear motor, nor do they greatly modify its basic shape. The methods are confirmed through on experiment and FEM analysis. This paper also discusses the effect of construction errors on cogging thrust.
This paper deals with the leakage current in an inverter system with a common-mode choke and grounding capacitors. In the conventional common-mode equivalent circuit, the leakage current does not depend on the position of the grounding capacitors. However, the characteristic of the leakage current in connecting the grounding capacitors between the common-mode choke and the rectifier is significantly different from that in connecting the grounding capacitors at the dc-link stage. This paper elucidates the reason why the leakage current in connecting the grounding capacitors at the dc-link stage flows only in the conduction period of the diode rectifier. The new equivalent circuit that reflects this phenomenon is proposed. Moreover, this paper shows the relationship between the positions of grounding capacitors and reduction effects of the leakage current based on a technique that the authors had proposed for an inverter system. The new circuit can also simulate the leakage current in the system using the proposed method.
In parallel boost converters, wiring loss occurs owing to the voltage difference between the converters. This paper proposes a wiring loss reduction method that employs CCM and DCM in a boost chopper. In particular, new approximation methods for the output voltage ripple of the DCM boost chopper are considered. Then, the carrier phase difference used to reduce the wiring loss is derived using the new approximation methods. Finally, the validity of the theory is confirmed by simulation and experimental results. The experimental results show that the wiring loss reduced to about 75% in the CCM and to about 65% in the DCM.
Working in extreme environments (e.g., working at disaster sites) is dangerous for humans. Hence, it is important to use teleoperated robots in such extreme environments. Because heavy lifting work is involved, hydraulic actuators of high output are more commonly used than electric actuators. Therefore, it is necessary to operate remotely controlled robots driven by hydraulic actuators. Bilateral control is remote control with the sense of force. Because most bilateral control systems have been studied mainly using electric actuators, bilateral control using hydraulic actuators is still a challenge. In this study, we propose placing a bilateral controller between an electric actuator on the master side and a hydraulic actuator on the slave side using the position and velocity. The controller exhibits the dynamics of bilateral control systems using the position and velocity. In addition, the control performance of conventional methods and the proposed method are compared and experimentally verified.
This paper describes a method to predict the life span of a die used for motors manufactured using a soft magnetic composite; in the study, a claw-teeth motor was used. The method involves performing stress analysis for a die and carrying out fatigue tests using test pieces. In the analysis, the soft magnetic composite was considered to be in powder form on the basis of its yield function, which was derived using a simple method. In addition to the analysis, we describe a simpler and more effective method in which the soft magnetic composite is considered to be a boundary condition. In the fatigue tests, we used test pieces that simulated the shape and construction material of the die. To predict the life span of the die, we evaluate the SN diagram, which represents the relationship between the maximum stress and fatigue life, with respect to the stress generated in the die. The life expectancy of a new die, which is about 100 rounds of use, is found to coincide substantially with its actual life. Furthermore, we explain how it is possible to extend the life span of a die to the targeted life span, i.e., more than 200,000 rounds of use, by changing its shape to reduce the stress.
In recent years, the demand for IH cooking heaters has grown as all-electric houses have become more common. The advantages of IH cooking heaters are high power, high efficiency, and safety. However, although the IH cooking heaters can heat a pan of iron or magnetic stainless steel, it is not effective for heating copper or aluminum pans. Aluminum pans account for approximately 30% of those used in homes. Therefore, IH technology that can be applied to heat all metal pans, including aluminum ones, is an important issue in terms of improving convenience. In this paper, we present a novel circuit topology for an IH system that is suitable for all types of metal pans. The proposed system changes the number of turns of the work coil according to the materials of which a pan is made, and changes the dc link voltage to add voltage to a single-ended push-pull (SEPP) high-frequency inverter. In magnetic pan heating, the proposed system controls the power through PFM control of the inverter, having reduced the number of turns of the work coil. On the other hand, in non-magnetic pan heating, the proposed system controls the power through PAM control of the dc link voltage, having increased the number of turns of the work coil.
This paper presents a detailed discussion on the modular multilevel cascade converter based on double-star chopper-cells (MMCC-DSCC). Hereinafter, it is simply referred to as the DSCC. A couple of DSCCs are used to form a three-phase 6.6-kV back-to-back (BTB) system installed between two power distribution feeders. Each DSCC, using 3.3-kV IGBTs, consists of 16 cascaded chopper-cells per leg. Low voltage steps bring about significant reductions in the harmonic voltage and current to the BTB system. A conventional power conversion system employs bulky line-frequency transformers and dc-link capacitors, whereas this system does not require either of them, thereby reducing the overall physical size and weight. Although no voltage sensor is installed on the common dc link of the BTB system, an indirect feedback loop in the control system makes it possible to regulate the mean dc-link voltage to its reference. This paper describes the design, construction, and evaluation of a three-phase 200-V, 10-kW downscaled model, with focus on operating principles and performance. Finally, experimental waveforms are compared with simulated ones obtained from a software package of PSCAD/EMTDC under the same operating conditions, including steady and transient states. The experimental and simulated waveforms agree well with each other.
Levitation characteristics of an electrodynamic suspension device using AC electromagnets driven by a high frequency current are influenced by the skin effect. The skin depth depends on the frequency of the exciting current, thickness of the nonmagnetic conductor, and electrical conductivity. The frequency that enables the levitation is estimated by measuring frequency characteristics of the lift force and the secondary copper loss and then calculating the temperature rise per second from the secondary loss when the nonmagnetic conductor thickness and electrical conductivity are changed. In addition, the thickness of the nonmagnetic conductor suitable for each drive condition is determined from the frequency characteristics. The measurement results of the frequency characteristics of the levitation device showed that the levitation frequency depends on the conductor thickness and the electrical conductivity. The results also show that the suitable frequency for each drive condition depends on the electrical conductivity of the nonmagnetic conductor.