Contact wires break because of the arc and large current flow generated between the pantograph and the contact wires when a train comes to a standstill at an insulated overlap. In this study, we confirmed the effectiveness of the function for putting out the arc of the compound catenary proposed as a countermeasure for this disconnection by on actual arc experiment. Moreover, we confirmed that the compound catenary proposed had predetermined current collection performance through simulation and traveling experiment. It was also it confirmed that the compound catenary proposed has a predetermined current collection performance also in the revenue line, and there was no influence on wear in the short term.

This study investigates the relationship between filter inductor impedance and dimensional resonance of MnZn ferrite. Experimental results clarify that multiple factors affect inductor impedance resonances. These can be classified into three factors: the inherent characteristics of a magnetic material, self-resonance due to winding stray capacitance, and winding that acts as a distributed constant line. Next, based on the measurement results, the dimensional dependencies of complex permeabilities (dimensional resonance) and the influence of dimensional resonance on inductor impedance are discussed in detail. Finally, this study verifies that the influence of dimensional resonance on complex permeability can be mitigated, and filter inductor impedance can be increased in the high frequency range by core lamination. All experiments are performed using off-the-shelf magnetic core products.

This paper proposes a novel modulation technique that reduces both motor acoustic noise and switching loss. The conventional discontinuous PWM method can reduce the switching loss to a greater extent compared to the conventional three-phase modulation method; however, the acoustic noise of the motor increases. The proposed technique adjusts the zero-sequence voltage given to the voltage references in such a way that the discontinuous part of the conventional discontinuous PWM method is changed smoothly. The switching loss with the proposed technique can be reduced to 58% of that with the conventional three-phase modulation method. The experimental results show that the acoustic noise can be reduced to a greater extent with the proposed technique compared to that with the conventional discontinuous PWM method.

Interior permanent magnet synchronous motor (IPMSM) has the disadvantage of many space-harmonic waves in air-gap flux density, leading to a large cogging torque. This study proposed a design method of a rotor structure with the notch for reducing the cogging torque of a double-layered IPMSM. The proposed method focused on the pulsating component of the cogging torque, which depends on the squared air-gap flux density (B_g²) of the motor. First, we analyzed B_g² of the motor without the notch using finite-element analysis (FEA), and the waveform of B_g² was approximated by a step waveform. Then, ideal waveform of B_g² was obtained theoretically so that the major components of the cogging torque can be zero. Based on the ideal waveform of B_g², we determined the notch position and width. Finally, we determined the optimal notch depth by FEA. The proposed method was applied to two types of IPMSM whose sizes, structures, and PM materials were different. The cogging torques of both the motors with optimal notches reduced significantly. Moreover, it also revealed that the notch hardly affects the maximum torque on load.

This paper presents a bidirectional non-isolated dc-dc converter based on three-level flying-capacitor converters intended to be applied to electric railway systems. It consists of several main converters with four power devices per converter, multiple auxiliary converters each of which is formed by cascaded chopper cells, and inductors for current control. The dc-dc converter can achieve zero-current switching (ZCS) for all the power devices in the main converters, not only under steady-state conditions but also under transient-state conditions including sudden changes in the supply voltage. This paper presents a current control method based on dq0 transformation and a voltage control method for the floating dc capacitors used in the auxiliary converters. The validity of the control methods proposed in this paper is verified through experiments using a 200-V, 2-kW downscaled model.

This paper proposes a method to design the search space of Model Predictive Control (MPC) for improving the steady current control performance of Permanent Magnet Synchronous Motor (PMSM) current control system. A current control system based on MPC predicts the future current behaviors for considerable input voltage and determines the optimum input voltage by evaluating these behaviors. However, the basic MPC has inferior steady current control performance depending on the operating points. This is because the search space of basic MPC represented by voltage vectors is not suitable appropriate for PMSM current control. To overcome this problem, we consider difference of search space of basic MPC and current vector control with a modulator such as Pulse Width Modulation (PWM) or Space Vector Modulation (SVM) and clarify the necessary search space for improving the steady current control performance. Then we propose a design method for the search space, and through experimentation, we show that proposed design method can improve the steady current control performance.

Vibration monitoring is effective for the early detection of equipment failure, and a vibration monitoring system for vehicle equipment has been developed from the viewpoint of enhancing the reliability and safety of railways. In the proposed system, abnormality detection is performed by applying the One Class Support Vector Machine (OCSVM) to the octave band analysis results of vibration. However, it is difficult to train OCSVM and optimize its hyperparameters for large-scale datasets due to limited computer resources. Therefore, we propose to combine prototype selection (PS) and OCSVM. In this paper, OCSVM is applied to actual vibration data, and the abnormality detection results and calculation time are compared with those of the conventional method. As a result, it was verified that abnormality detection equivalent to that of the conventional method can be achieved using OCSVM with PS.

Iron losses generated in a motor made of non-oriented electrical steel and driven by an inverter consisting of fast switching power semiconductor devices, GaN-FETs were studied. The rectangular voltage pulses from the pulse width modulation applied to the motor generate not only a fundamental current but also harmonic currents. One of them increases considerably at the resonant frequency of the L, R, and C components in the motor. The phenomenon is called ringing. The ringing current, as well as the other currents, result in their respective iron losses. This study experimentally confirms that ringing occurs in the motor and quantitatively evaluates the iron loss related to it. The proportional dependence of the loss on the carrier frequency of PWM is found out.

Three-phase capacitor input diode rectifiers offer several advantages such as a simple topology, low high-frequency noise, high reliability, and high environmental durability. However, they produce undesirable lower-order harmonics in the input current. To overcome this problem, a three-phase diode rectifier without active switching devices or transformers is proposed, which meets the regulations of JIS C 61000-3-2 (Class A). In this paper, the proposed rectifier (7.0kW, 200V/50Hz) is validated through experimental results.

In recent years, local intense rainstorms that are difficult to predict until just before the occurrence (about 30 min before) have been occurring more frequently, resulting in a higher risk of trains being interfered with, or even caught in a flash flood. This paper introduces a method to determine the optimal stopping position for trains to avoid such flash floods, with a reasonably fast mathematical optimization calculation. The method provides decision makers with informative solutions applicable to train operations on a quantitative basis when a local intense rainstorm is predicted.

This research group focuses on the generating, converting, transferring, and consuming electric power in marine large vessels and underwater vehicles.