In this study, a Solitary Wave Track Circuit (SW-TC) is developed, which sends the wave source by a fixed number as signal waves within a cycle, instead of sending continuous signal waves in the track circuit. The SW-TC has a simple configuration and can deal with a lot of information by utilizing the spacing between wave sources as information. In this set-up, the expansion of information quantity and function improvement is made possible by transmitting the start element which connects two solitary waves at the beginning of one cycle frame. In addition, this paper presents the switching control methods of the transmission reception parts of a track circuit, and the switching control methods of an up-signal and a down-signal, which are required at the point of change of traffic direction, in a single track line. Moreover, a new train control function that is equivalent to a conventional digital ATC is outlined.

Power electronics systems have significantly contributed to energy saving by high power conversion efficiency. Some characteristics of power devices have played an important role. Recently, wide-bandgap power devices, such as gallium nitride (GaN) and Silicon carbide (SiC), have been developed for next-generation circuits, owing to their high breakdown field and mobility. GaN power devices can switch at higher speeds compared with SiC power devices.

In this paper, we present the results of the influence of PCB stray inductance on the switching performance of the cascode connected GaN power device in TO-247 package. The stray inductance is calculated from electromagnetic field analysis. Two half-bridge circuits which have different stray inductance are evaluated by switching test and boost-chopper with DCM control.

To estimate in advance the high-frequency impedance of a motor, and its internal voltage distribution when an inverter surge is applied, a technique to derive the circuit constants of various parts of a motor based on electromagnetic field analysis and build its high-frequency equivalent circuit, where each turn of the coils is separately modeled, has been developed. By switching between 2D and 3D analyses and between 1-slot and 1-pole models to accelerate the calculation method and by automating them in parallel, the developed technique even enables non-experts to build an accurate high-frequency equivalent circuit of a motor. Based on the accuracy verification, the shared voltage of coils can be estimated with an error of 20% or less by considering the frequency characteristics of the resistance and inductance of each turn of the coils and modeling a lead wire in the measurement setup.

This paper presents an operation verification of a proposed gate drive circuit with a condition monitoring function for silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs). The proposed gate drive circuit has an in-situ measurement function of the input capacitance of SiC MOSFETs to detect gate oxide degradation, which is an issue affecting the long-term reliability of SiC MOSFETs. This study demonstrates, both theoretically and experimentally, that input capacitance is an aging precursor suitable for condition monitoring. In addition, experimental verification of the gate drive at a switching frequency of 20kHz and the in-situ measurement function of the input capacitance as condition monitoring are demonstrated for a 1.2kV SiC MOSFET.

This paper proposes a small and high efficiency circuit topology for series connected devices with regenerative snubber circuits. The proposed circuit topology introduces an important break-through in the trade-off between switching losses and dv/dt. Regenerative snubber circuits store most of the switching losses that occur in general circuits and regenerate at high efficiency. A 10kW-200V class prototype of the proposed circuit topology recorded a maximum efficiency of 99.49%, and a rated efficiency of 99.21%. Loss analysis of the prototype demonstrated no reduction in efficiency due to the regenerative operation by regenerative snubber circuits.

This paper proposes a measurement method of parasitic components in a PCB for a high-frequency and high-voltage inverter circuit. The proposed method enables accurate measurements by using a VNA port extension and a 50Ω microstrip line. Parasitic components can be extracted accurately by considering the uncertainty in S parameter measurements.

In our laboratory, we are researching the gate control of semiconductor devices and the technology to extract electric power without contact. This paper introduces an overview of our research.