Electrical Engineering in Japan最新文献

Accurately calculating the transmission-line constants of underground cables is important for various types of power system simulations such as electromagnetic transient, power flow, and transient stability simulations. The transmission line constants of cables installed in a tunnel must be calculated taking the skin and proximity effects into account, since the cables are spaced closely to each other and also to a wall face of the tunnel. However, the conventional method, which is capable of considering the skin and proximity effects, has been restricted to circular cross-section conductors such as cables and a circular tunnel. Therefore, the method cannot handle a tunnel with a rectangular cross section. In this paper, a method for calculating the transmission-line constants of a conductor system in which both circular and rectangular cross-section conductors present in the same space is proposed. Then, the walls of a rectangular tunnel are represented by eight rectangular conductors, and cables represented by circular conductors are placed inside the eight rectangular conductors. In this paper, the proposed method is verified by experiments using a conductor system in which three circular conductors are arranged in a rectangular conductor. Calculated results obtained by the proposed method agree well with the measured results.

This paper proposes a new gradient driver with a gradational voltage inverter for low power loss and downsized filter circuits. Gradient drivers produce direct current with low ripple amplitudes to achieve high image quality and high slew rates to obtain images rapidly. The proposed gradient driver is characterized by low ripple amplitude of the output current from the inverter composed of SiC-MOSFETs and high output voltage from another inverter composed of IGBTs. This paper discusses both the principle of operation and control method of the new gradient driver. Experimental verification is performed on a full-scale system. The results show the advantages of the proposed gradient driver based on loss analysis by calculations.

Contact-force control of propeller-driven systems achieves aerial tasks that require contact motions with objects. Conventional contact-force controllers for propeller-driven systems utilize a contact-force feedback controller. Although the feedback gain should be high to achieve high target tracking performance, a high gain causes a large overshoot. This paper therefore proposes a novel contact-force controller which utilizes an airframe's velocity and an airframe's acceleration. An estimated acceleration and an estimated velocity of the airframe are fed back to the contact-force controller. A rotor angular velocity is utilized to estimate the acceleration. The validity of the proposed controller is verified through frequency analysis, simulation, and experiment.

With the goal of establishing a new cancer treatment method using nanosecond pulsed electric fields (nsPEFs), we investigated the effect of applying nsPEFs and anticancer drugs (adriamycin, ADM) to cancer cells. The surviving fraction of cancer cells was significantly reduced by nsPEFs application compared to the control. Compared to nsPEFs alone and ADM administration alone, a significant decrease of the surviving fraction was observed in combination of nsPEFs application and ADM administration. In addition, multiplying value of surviving fractions of nsPEFs application and ADM administration was calculated as a pseudo-combination effect. The surviving fractions of the experimental combinational results of nsPEFs and ADM were lower than the pseudo-combination results. Therefore, the synergistic effect of combination of nsPEFs and ADM was confirmed. Furthermore, the surviving fraction of ADM administration after nsPEFs application was significantly lower than that of ADM administration on 24 h before nsPEFs application. ADM action on cells would be effective owing to nanopores were formed by applying nsPEFs. It was confirmed that ADM and nsPEF induced apoptosis of cells from apoptosis and necrosis test using FACS.

Laborsaving is a major issue in production. In an automotive production line, a yard that is used as a temporary storage for vehicles before shipping. The vehicle-loading robot that operates autonomously has been proposed to automate the alignment of vehicles in the yard instead of human driving. In this study, the dynamic wireless power transfer (DWPT) system that includes the structure of the roadside for the vehicle-loaded robot is proposed. It is proven that the transmitter coil has enough durability for the load of the robot weight using simulation and actual measurement. It is also shown that the reinforcement bars of the road structure cause considerable eddy current loss even with stainless steel. This is similar to loss by coil resistance. This system achieves a 1.8 kW DWPT with an automated coil detection system and a frequency control system, under factory conditions.

This paper comprehensively evaluates the PV power smoothing control method using the spline function. As a result of the verification, it is shown that the ESS capacity can be reduced while maintaining the smoothing effect by PV power smoothing control with energy control and limiting fluctuation rate control. Based on the charging/discharging power of the ESS and the operating conditions of the ESS, the section time that achieves both improvement of the smoothing effect and reduction of the ESS capacity is determined to be 1500 s. Then, the rated capacity of the ESS for a rated power of 1.75MW PV system is 1128 kWh. This is 49.6% of the rated capacity of the ESS, which is required in the PV power smoothing control method with fluctuation rate control. As a result of comparing the proposed method and the moving average method, the proposed method improved the smoothing effect by 49.8% compared to the moving average method.