This paper describes the power efficiency and losses in push-pull MOS-FET arrays in an inverter for a plasma generator. The inverter consists of parallel connected MOS-FETs and the output power transformer. The power losses within the MOS-FET arrays and output power transformer are estimated based on their thermal resistances, which were obtained separately by measurements. The drain efficiency was thus obtained from the DC input power, RF output power, and estimated power losses. The output power of the MOS-FET arrays was 1kW, with a drain efficiency of 79% and at 13.56MHz, when the DC voltage was 48V.

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Since electric vehicles (EVs) suffer from a long charging time and a short mileage, they have not yet formed a full-scale market. A dynamic wireless power transfer system that can supply electric power to the vehicles during driving has been expected as an effective means to solve the above issues. When the primary coils are connected in series, the dynamic wireless power transfer system becomes the same in equivalent circuit as a stationary wireless power transfer system. As a result, the dynamic system is of great advantage for the common use of the secondary coils for parking and driving. This paper provides a fundamental discussion on the dynamic wireless power transfer system with focus on the secondary coils, along with experimental results.

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An analysis of the minimum peak phase current maximum torque of the dual winding motor is presented in this paper. In general, the maximum current determines the size of the motor and the chip size of the switching devices, since the rise in temperature is greater if there is more current. To lower the maximum current, the minimum current required to generate a predetermined torque without increasing the torque ripple using cancellation of the torque ripple generated by the two windings was analyzed. The high harmonic current, which does not generate torque ripple in the dual winding motor, is explained, and the minimum current required to generate a predetermined torque using the high harmonic current is presented. The results of the experiments that were conducted to confirm that the maximum current is lowered without increasing the torque ripple are also presented.

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This paper presents a high-frequency isolated AC/DC converter using the soft-switching technique. The AC/DC converter consists of a matrix converter for transforming three-phase AC voltage to high-frequency AC voltage, a high-frequency transformer and an AC/DC rectifier. In order to reduce the switching loss, soft switching at every commutation of the matrix converter and AC/DC converter is achieved. The effectiveness of the proposed converter and the control scheme was verified by experiments.

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In this paper, an angle detecting system is proposed that calculates the offset correction values for the sine and cosine signals of angle sensors. The offset correction values are calculated not from the offset errors of the sine and cosine signals but from the 1f angle error (the fundamental frequency component of the sine and cosine signals) of the angle signals. Therefore, the system can correct the 1f angle error even when the sine and cosine signals contain the double-frequency components of the sine and cosine signals, as well as the DC offset errors. Moreover, it is possible to use low-cost microcomputers with low computing speed, because the offset correction values are DC quantities.

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“Global warming” which is caused by the increase in greenhouse gases as a result of human activities' such as fossil fuel burning and deforestation to increase production etc., leads to higher average temperatures of the earth's near-surface air and a variety of abnormal phenomena. We must therefore realize new technological innovations that are environmentally friendly as soon as possible. A final goal toward achieving a zero pollution society is to utilize electricity produced by renewable energies' such as biomass fuels. The Stirling engine can produce mechanical power and electricity from any heating source and thus allows to reduce “Global warming” by using renewable energies. However there are few applications that allow electricity to be obtained via the Stirling engine directly from biomass fuels. In this paper we describe in detail a fundamental electrical characteristic of the Stirling engine generator with a series resonance circuit, connected to a power line. The results of experiments and the proposed approximation model show optimal operation giving maximum output power and a higher power factor. The results provide important information and guidelines for practical applications of the Stirling engine generator.

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In recent years, the response to a ground fault in a power facility has consisted of insulating the electrical circuit using the ground relay. However, this method does not determine the cause of the ground fault. In this study, focusing on three major causes of a ground fault, “tree contact”, “wildlife contact”, and “insulator deterioration”, we determine the cause by using a new decision method. The decision method proposed in this study can determine the ground-fault cause with high accuracy by using the characteristic of the ground-fault current waveform shape of each ground-fault cause, and thus, it is possible to construct a sophisticated energy supply and demand system.

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A model for a Personal Rapid Transit (PRT) system is proposed, using an embedded Markov chain to manage traffic behavior at a grade separated interchange. The interchange is composed of a main line and a subline. There are two kinds of vehicles in both the main line and the subline, respectively; these are branch vehicles and straight vehicles. A vehicle on the main line has priority. Thus, a queue is formed only on the subline. Waiting times of subline vehicles are restricted to a fixed value. If the waiting times exceed the value, a vehicle will be detoured. This value is called the restricted entry waiting time. We analyze the embedded Markov chain model according to the generating function technique. The relationship between the value of the restricted entry waiting time and traffic behavior is examined; the obtained results clarify how to decide the optimum value of the restricted entry waiting time.

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This paper proposes an online-type decentralized controller tuning method for the decentralized control system of a web transfer system, in which the mutual interactions are significant. The controllers are updated online by employing the fictitious reference iterative tuning (FRIT) and the online particle swarm optimization (OPSO) methods based on the structure of overlapping decomposition. It is demonstrated experimentally that the combination of FRIT and OPSO can improve the control performance with time using the test bench.

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The interest and effort invested in developing a motor with multiple degrees of freedom (DOF), which by itself can directly drive motion in multiple directions simultaneously, are increasing. Such motors are intended for use in industrial applications having increasing complexity and performance demands. Active research is being conducted on linear motors with two DOF, driving linear and rotational motion simultaneously, for application in multiple-DOF positioning systems. We aim to develop a medium-sized rotary-linear motor (RLM) with a few or more kilowatts power and with capacity for rotational and translational motion. Here, we present a method for installing a salient pole on a needle with magnets, which can enable the use of soft magnetic materials with low eddy-current loss as the iron cores. We demonstrate the installation method for a salient pole that generates reluctance electromagnetic forces in one or both directions: rotational and translational. This study demonstrates the effectiveness of the salient pole in increasing the electromagnetic force. We also introduce a mathematical model of RLM with a salient pole on a dq coordinate system. The model is used to explain the interactive magnetic interference generated by the armature currents for rotational and translation motion. A test motor is used to verify the effect of the salient pole, estimate the eddy-current loss, and examine the spiral motion due to the rotational and translation motion.

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This paper presents a new hybrid dc circuit breaker producing no conducting power loss under normal operating conditions and having the capability to interrupt a large amount of short-circuiting current within several milliseconds. It consists of two reactors for current limiting and current control, two mechanical contactors, and a multilevel converter based on the cascade connection of multiple full-bridge dc/dc converter cells. It is characterized by achieving current commutation from the main mechanical contactor to the multilevel converter with fast current control. This results in eliminating auxiliary power semiconductor switches that produce a non-negligible conducting power loss under normal operating conditions. This paper discusses both principles of operation and control method of the new hybrid dc circuit breaker. Experimental verification is performed by a downscaled system rated at 300V and 150A, along with verification by computer simulation.

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This paper proposes a permanent magnet synchronous motor (PMSM) control strategy based on open-loop control. Low-frequency torque vibration excluding the sixth- or twelfth-order harmonics occurs because the voltage fluctuates from the transition to the square-wave voltage. Therefore, the proposed control uses a variable band-pass filter to reduce low-frequency torque vibration. In the experimental results, the low-frequency q-axis current decreased by approximately 50%.

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Our laboratory focuses on power electronics, especially a variety of power converters and electric machinery. Recently, various studies on novel circuit topologies of the multilevel power converters and the switching assist technologies are intensively investigated among us. On the other hand, many kinds of the rotating machines are under development. A great emphasis is placed on the system implementation and the experimental tests as well as the theoretical analyses and the computer simulations in research process of the both fields.

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