Since a motor drive system contains an inverter (high-voltage circuit) and gate drive circuits (low-voltage circit) with a switching regulator, electromagnetic noise is generated in each of these two circuits, and noise interference between these circuits can occur. This paper discusses noise interference between the high- and low-voltage circuits of an electric compressor system with an integrated mechanical and electrical structure. Analysis using LTspice shows that the experimental and analytical results are in good agreement when a very small stray capacitance occurs between the high- and low-voltage circuits. An experiment using an actual compressor showed that conducted noise above 20MHz can be reduced by up to 10dB by reducing the effect of stray capacitance between these circuits.

The authors proposed a unidirectional isolated secondary-resonant single-active-bridge (SR-SAB) DC-DC converter. The proposed SR-SAB converter consists of an H-bridge circuit, a high-frequency transformer, and diode-rectifier circuit with a resonant capacitor connected to each diode. It can produce waveforms similar to that of a dual-active-bridge converter by using the resonant capacitors. Therefore, the SR-SAB converter is a unidirectional isolated DC-DC converter for high-power applications. Single-leg and double-leg resonant circuits are the two circuit topologies of the SR-SAB converters. The resonant capacitor is connected to only one leg of the diode-rectifier circuit in the single-leg resonant circuit, and to both legs of the diode-rectifier circuit in the double-leg resonant circuit. In this paper, the operating theories and characteristics of the single-leg and double-leg resonant circuits are analyzed and compared. The effectiveness of the analysis is experimentally verified using 4-kW laboratory prototypes.

For the purpose of reducing the electricity cost, we conducted a trial manufacturing of a device that switches the winding connection of a drive motor during operation, and performed a durability test on it. The contact resistance value was initially set to 0.32mΩ. The measurement results showed that the resistance value of the contact with the longest lifetime was 1mΩ or less, up to approximately 80,000 cycles. The variation in lifetime is attributed to the difference in the direction in which the gravity of the short circuit plate is applied to the contactor. To address this issue, we developed a countermeasure by changing the contactor from a flat plate shape to a cylindrical shape. When we applied a mechanical switching device similar to this prototype (contact resistance value equal to 1mΩ), the calculations showed that the electricity cost reduced by 4%.

To minimise the deterioration of acceleration/deceleration performance of railway vehicles under low adhesion conditions, various kinds of slip controls have been developed. However, the theoretical systematization of wheel slip controls has not been discussed sufficiently as they are developed individually. This paper systematizes wheel slip control technologies based on excessive torque and angular momentum theories that have been proposed in one of the wheel slip re-adhesion control methods.

In recent years, environment perception systems have been developed to achieve autonomous operation of existing railways. To make the system reliable, fusing multiple sensor data is effective, and the sensors have to be calibrated for the sensor fusion. In this study, we propose a method to calibrate a LiDAR and a monocular visible light camera using rail detection results. By utilizing existing rails as targets, our proposed method does not require any new target installations and can carry out calibration before the train starts running. Considering some of the rail shape features, rails can be robustly detected using LiDAR data. With the camera, 2D rails are detected by referring to an existing method and converted to 3D rails. Extrinsic parameters of a sensor are calculated by using the point correspondence of the detected rails in different coordinate systems. Experiments showed that our method reduced the object location error due to inappropriate extrinsic parameters, and the estimated parameters were more accurate than another known method in use.

Power Engineering Laboratory at Nagaoka University of Technology conducts research on the application of power electronics to power systems. The laboratory investigates virtual synchronous generator controlled inverters, ac/dc hybrid microgrids, rotating heat generators, and other power applications through simulation and experiments.