Ultrashort electromagnetic pulses (0.45ps time width) are radiated into free spece from high-T_c superconducting films fabricated into antenna structures by exciting with ultrashort laser pulses. The Fourier spectrum of them extends from 0.1 to 3THz. Basic characteristics of the radiation are studied, including the dependence on the bias current, external magnetic field, exciting laser power, etc. Possible applications of this new phenomenon to high speed wireless communications, characterization of materials and memory devices are also presented.

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Recently, the nonlinearity of the switching system is widely interested. Especially the analytical problem appears at the connection of state space. That is, power electronics circuits lose the continuity of the state at the switching instant. However, most of the analytical method cannot deal with the problem if they are based on the analysis of the continuous system. In this paper, a new method, hybrid system theory, is induced to describe the switching dynamics of power electronics circuit.

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The current source AC/DC converter with energy recovery snubber circuits has been expected for applications of superconducting magnetic energy storage and DC transmission system because of its high efficiency and easiness for large capacity. In this paper, characteristics of this AC/DC converter under the sinusoidal pulse width modulation control were studied by both computer simulation and experiment. The characteristics were compared with typical current source type PWM converter on converter losses and distortion of AC current waveform.

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Inverters employed in welding power supplies for using overseas demand to attend requirement such as application to a wide range of world voltage and regulations and competitive cost.
This paper presents examples of structure, circuit configuretion, and product development.

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It is necessary for converter design to analyze its operation modes completely. However series-resonant type DC-DC converter (LC type) is difficult to analyze because it has several operation modes. Especially a link transformer is modeled with its parasitic elements, it has been reported that it has more operation modes because L and/or C elements are added. This report analyzes the converter with the parasitics (LCC, and LLCC types) for its operation modes and the results are investigated to make clear its operation behaviors by a operation mode analysis software developed by one of the authors and by SPICE. This method and results are also useful for analysis of series resonant converters (LCC, LCL, LLCC types).

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Recently, synchronous motor using reluctance torque is drawing the attention. Especially interior permanent magnet synchronous motor (IPM motor) is widely used for several industrial applications such as a compressor drive and an electric vehicle. However, the efficiency of IPM motor decreases at high speed and light load operation. Such problems can be improved by reducing magnetic flux and increasing reluctance torque. In this paper, we experimentally investigate machine performances of SynRM and IPM motors, including IPM mainly using reluctance torque. And we analytically examine efficiency characteristics of IPM motors at high speed and light load operation.

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The author propose two types of harmonic reducing 3-phase-bridge diode-rectifiers consisting of single or double parallel conventional 3-phase-bridge diode-rectifier of capacitor-input type and an auxiliary circuit. In double 3-phase-bridge type, harmonics of the total input current are remarkably reduced by connecting the midpoint on dc-side to the neutral point on the 3-phase ac input side. The midpoint on dc-side is provided by using two dc-capacitors connected in series between upper and lower dc-rail, while the neutral point is provided by using zigzag auto-transformer if isolation between the ac-side and the dc-side is not necessary and a delta-star isolation transformer is not available. In single 3-phase-bridge type, the harmonic reducing principle in the double-bridge type is applied by adding low rating diodes to the auxiliary circuit. Since both the proposed harmonic reducing rectifiers do not require a self-turn-off device nor a controller, the proposed diode rectifiers are very economical, efficient and reliable. Therefore, the new rectifiers of single-bridge type and double-bridge type are suitable for low to medium and medium to high power applications, respectively.
This paper describes the unique arrangement and the particular operation of the proposed rectifiers and then, the performance is evaluated through simulation results for double-bridge type and a experimental results for single-bridge type.

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We developed a new light-weight power-assisted bicycle using a giant magnetostrictive torque sensor, which is a new mechatronics product for individual use. The key components for power-assisted bicycles are sensors, which are vital for detecting the extremely large forces (maximum crank axle torque: about 160Nm) of power exerted on the pedals by the riders. In this paper we propose a torque detection method that uses a giant magnetostrictive material with a high force detection sensitivity, where the capacity to resist stress is extremely large.

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