To calculate carbon dioxide (CO2) emission for studying CO2 reduction in railway transportation towards net-zero carbon emissions, this study develops an energy consumption estimation method for long-distance train. To estimate losses such as running resistance loss, this method does not simulate the speed profile of the train but assumes that its running speed is constant at its average speed. A calculation method of energy losses caused by braking due to downhill and speed limits is developed to improve the accuracy of energy consumption estimation. Those braking energy losses are calculated systematically as mechanical energy by using track and timetable data. Measured energy consumption of freight trains and the results calculated by the method developed are compared. The calculated results differ from the measured results within an error of approximately 10%.
In some sections of simple-support bridges, fatigue failures of wire in overhead contact line systems are caused by large bridge oscillations generated by passing trains. Our study reveals the condition under which the amplitude of overhead contact line system oscillations becomes large, by analyzing coupled oscillations of bridges and catenary poles generated by passing trains. To prevent the fatigue failures of wire in overhead contact line systems caused by large bridge oscillations generated by passing trains, a pole vibration suppression band and a new metal fitting are developed. Moreover, a decision-making flowchart is developed to determine the necessity of measures.
We developed a torque stabilization method for the regenerative operation of speed sensorless vector controlled induction motor (IM) drives. Speed sensorless vector control suffers from a torque reduction phenomenon in regenerative operation. Therefore, we analyzed the cause and developed two stabilization methods: one to stabilize the decrease in IM flux and the other to adjust the velocity command in the low-speed range. Time domain simulations and experiments demonstrate the effectiveness of the proposed method.
This paper explores, the adoption of a series slave drive for discharge switches to reduce the costs of discharge circuits in high-voltage power supplies for ERF dampers. With this driving method, the charging period of the voltage divider capacitor after the turn-off of the discharge switch is a dead time, which reduces the responsiveness of the system. Thus, a control method to reduce the dead time by turning-off the discharge switch at a higher output voltage than the target was proposed. This method is based on the estimated charge energy of the voltage divider capacitor and the estimated energy consumption of the load with high temperature dependence of the parameters. The circuit was simulated to verify the effectiveness of the proposed control for reducing dead time in the range of discharge voltage amounts from 1kV to 4kV. As a result, the switching cycle of the discharge circuit was reduced by up to 23% at an ERF temperature of 20°C and up to 38% at an ERF temperature of 50°C by reducing the dead time with the proposed control. This confirmed the effectiveness of the proposed control.
Lithium-ion batteries (LIBs) in electric vehicles at low temperatures need proper pre-heating to avoid a decrease in their discharge capability. Internal ac heating techniques utilizing Joule heat generated by ac current flowing through an internal resistance of LIBs have been proposed as an efficient heating method. However, an additional inverter is necessary to generate ac currents, increasing system complexity and cost. Furthermore, traditional internal ac heating techniques using triangular or sinusoidal current waves are not ideal due to their relatively low rms values at a given peak current that eventually result in slow heating. This paper proposes a novel internal ac heating technique utilizing an existing inductor in ordinary dual active bridge (DAB) converters that are typically employed as an on-board converter. Depending on modulation techniques, the proposed converter can generate four types of trapezoidal current waves with different rms current values, all of which achieve shorter heating time than conventional internal ac heating. A charge-discharge power rating of 700W prototype with 40-W internal ac heating capability was built for a 48-V LIB. The experimental results demonstrated the proposed converter could heat up the LIB from -10°C to 0°C in 3.3 min.
Simple and cost-effective methods for cavitation detection are required for the stable operation of pump systems. Previous researches on cavitation detection systems have used microphones or vibration sensors, however they are costly and difficult to install. Recently, motor current signature analysis (MCSA) has been gaining attention with regard to motor fault detection. In this paper, we review the characteristics of motor current signals in a cavitation state and propose an MCSA technique for pump cavitation detection. We observed that the foot around the fundamental harmonic spectrum in the power spectral density (PSD) of current signals increased in a cavitation state. Based on these results, we propose defining an evaluation value that reflects the foot and using it for cavitation detection.
Single-phase capacitor-input diode rectifiers have several advantages, including simple topology, low high-frequency noise, high reliability, and high environmental durability. However, these rectifiers produce undesirable lower-order harmonics in the input current. To overcome this problem, the authors proposed a new single-phase capacitor-input diode rectifier that meets the harmonic limits specified in “IEC 61000-3-2 (Class A)”. In this letter, the transient responses of the proposed rectifier were evaluated based on experimental results from a functional prototype, and it was confirmed that no overvoltage or overcurrent conditions occurred in the passive components.