Electrical Engineering in Japan最新文献

Currently, no technology has been established to measure the amount of ocean microplastics (MP) less than 5 mm. As a basic study of the quantitative evaluation, the authors proposed measurement method using the attenuation of transmitted light for the amount of microplastic that concentrated by dielectrophoresis. In this study, we report effective collection method of microplastics by combining an electrode structure that generate negative dielectrophoresis and a driving method using additive Synthesis sine wave.

Battery Energy Storage Systems (BESS) are compatible with renewable energy, so they are becoming increasingly popular around the world. On the other hand, the number of fire accidents are increasing with the spread of batteries, and as a result of the author's own analysis of these fire accidents, the author found phenomena unique to BESS fires. Therefore, the author will investigate whether Japan domestic laws and regulations are compatible with these unique phenomena and propose necessary safety countermeasures.

Characterizations of pulsed power output for pulsed power generator using GaN FET have been evaluated and compared with using SiC-MOS FET. The fast rise/fall time of output voltage without the dependance on the dummy load has attractive feathers. However, the surge voltage between drain and source terminals, exceeding the maximum rating occurred due to the fast turn-off speed feathers of Gallium nitride (GaN) FET, which has limited the power capability. The inductive energy storage pulsed power generator using GaN FETs as opening switches has developed, and the output obtains a maximum voltage of ∼900 V with rise/fall time of <20 ns. The fast current interruption characteristics by the turn-off of GaN FET lead to high voltage-pulsed output.

In this paper, a method for extracting constant power from transformers on power lines is presented. The secondary side power equation is obtained based on the circuit equation for power superposition using a single-phase transformer. Using this equation, an area discrimination method of the speed versus torque characteristics of the permanent magnet synchronous motor and a power superposition control method in the area are proposed. To validate the proposed method, the discrimination method was verified via simulation and experiment with boundary conditions. Similarly, the power superposition control method was verified via simulation and experiment, with the command current controlled using a power estimator. The results verify the discrimination and power superposition control methods.

If a voltage dip gets lower than a certain threshold at the moment when a transformer is energized, its mitigation is required. For this reason, when a transformer is energized, the voltage dip is calculated in advance and the need for its mitigation is considered. From the viewpoint of preventing unnecessary countermeasures, highly accurate calculations are required. However, electromagnetic transient analysis, which is known as a method with high accuracy, is not practical because its operation is rather complicated. In this paper, the analytical circuit is simplified by simulating the magnetizing inductance of the transformer with the inductance and the series connection of the ideal switch, and analytical formulas for the flux and current in the winding are derived for each switching mode. The calculated inrush currents and voltage dips during transformer energization using the derived analytical formulas agreed well with the results from electromagnetic transient analysis, which handled the nonlinear current-flux characteristics precisely.

One of the models for rotating machines, such as synchronous machines and induction machines, is the phase-domain model, which is characterized by formulating the circuit equations of the rotating machine in the phase domain and solving them simultaneously with the external system to which the rotating machine is connected. Although this model has excellent numerical stability and calculation accuracy, it requires refactorization of the subcircuit that includes the rotating machine at each calculation time step, which degrades the calculation speed. This paper describes the results of an attempt to improve the calculation speed when using the phase-domain model by using partial refactorization, which makes the refactorization process more efficient.

In recent years, a demand for smaller traction motors with higher power has arisen. This study focused on high-speed rotation for miniaturization and developed a prototype motor using Nd-based bonded magnets. It had a maximum rotational speed of 34,000 rpm, which is twice that of existing 50 kW-class motors. The motor achieved the desired performance in the test in combination with a reducer. As a result, the weight of the prototype motor was reduced by 54%, and a power density of 6.7 kW/kg was achieved.

Technical innovations for the downsizing of motor systems are necessary to realize energy savings and roomy and comfortable car interior space in electric vehicles. In this paper, a novel motor drive system with multiple high-speed motors and a magnetic multiple spur gear (MMSG) is proposed for electric vehicles. Furthermore, the factors leading to a high-power density and high torque density in an MMSG system are clarified.

This paper addresses drone controller design with 3D target trajectory and presents a backstepping-based controller taking into consideration the integral of tracking error. Performance evaluation is performed in situational and experimental environments, and the advantage of the proposed scheme is illustrated in the comparison with the conventional backstepping and the Proportional-Integral-Differential control. The experiment results show that the proposed scheme exploiting the integral of tracking error can reduce steady-state error. Furthermore, they show that introducing a reference model experimentally improves the tracking performance for a given target trajectory.

The paper presents a new fault location method with traveling waves (surge) on distribution line to restore power supply as soon as possible. The proposed method builds a diagram that describes transmission and reflection of traveling waves over the lines and generates pseudo waves based on the diagram. The least error condition including fault point is estimated by numerical analysis comparing measured waves and pseudo waves. The method is robust and accurate without line parameters such as the speed of traveling waves. The method can be applicable for multiple faults and branch line faults without any additional modification.