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168 results on '"Kawamura, Wataru"'

24. A Low-Speed, High-Torque Motor Drive Using a Modular Multilevel Cascade Converter Based on Triple-Star Bridge Cells (MMCC-TSBC)

Author

Kawamura, Wataru, CHEN, KuanLiang, Chen, Kuanliang, Hagiwara, Makoto, and Akagi, Hirofumi

Subjects
Engineering, Universal motor, Vector control, business.industry, Power factor, AC motor, Industrial and Manufacturing Engineering, Cascade converter, Motor drive, Direct torque control, Control and Systems Engineering, Control theory, Electrical and Electronic Engineering, business, Induction motor
Abstract

This paper provides experimental verification of a modular multilevel cascade converter based on triple-star bridge cells (MMCC-TSBC) for a low-speed, high-torque motor drive. The TSBC is one of direct ac-to-ac power converters capable of achieving bidirectional power flow and drawing/feeding three-phase sinusoidal input (supply-side) and output (motor-side) currents with any power factor at both sides. This paper designs, constructs, and tests a downscaled drive system combining a 400-V, 15-kW, phase-shifted-carrier PWM TSBC equipped with four bridge cells per cluster and a 320-V, 38-Hz, 6-pole, 15-kW induction motor loaded at the rated torque. Experimental waveforms obtained from the downscaled drive system verify stable operation across a broad range from a standstill to the rated speed, showing satisfactory start-up performance.

Published
2015

25. Generalized Power-flow Analysis and DC Capacitor-Voltage Control of the Modular Multilevel Cascade Converters Based on Star Configuration (MMCC-xSBC)

Author

Kawamura, Wataru, Hagiwara, Makoto, and Akagi, Hirofumi

Subjects
モジュラー・マルチレベル・カスケード変換器, パワーフロー解析，直流コンデンサ電圧制御, Modular multilevel cascade converter, power-flow analysis, dc-capacitor-voltage control
Abstract

The modular multilevel cascade converter (MMCC) family has been attracting attention from power electronics and power system engineers because it has been showing considerable promise as one of the next-generation high-power high-voltage/medium-voltage power converters. This paper provides an intensive discussion on power-flow analysis of three MMCC members with star configuration, focusing on dc-mean-voltage balance/regulation and ac-voltage mitigation control of all the floating dc capacitors. Most existing analysis methods are based on single-phase circuits, which make it difficult to derive capacitor voltage regulation/mitigation methods relying only on circulating currents and zero-sequence voltage. The power-flow analysis and regulation/mitigation methods developed in this paper are characterized by applying the αβ0 coordinate transformation(s). The validity of the power analysis and the regulation/mitigation method is confirmed by simulation using the PSCAD/EMTDC software package.

Published
2015

28. Decoupled Control of a Modular Multilevel Cascade Converter Based on Triple-Star Bridge-Cells (MMCC-TSBC)

Author

Kawamura, Wataru and Akagi, Hirofumi

Subjects
Modular multilevel cascade converter, medium-voltage motor drives, ac-to-ac power conversion, モジュラー・マルチレベル・カスケード変換器, 高圧モータドライブ, 交流/交流変換
Abstract

This paper presents a modular multilevel cascade converter based on triple-star bridge-cells (MMCC-TSBC) with a focus on its decoupled control. The TSBC is one of the direct ac-to-ac power converters having the capability of bidirectional power flow with three-phase sinusoidal input (supply-side) and output (motor-side) currents. Therefore, it is suitable for a medium-voltage motor drive requiring regenerative braking. This paper has an intensive discussion on control strategy for the TSBC, which includes current control, capacitor-voltage-balancing control, and fluctuation-mitigating control for low-speed operation. This control strategy succeeds in achieving decoupling among supply (input) currents, motor (output) currents, and circulating currents, using the αβ0 coordinate transformation. The validity and effectiveness of the control strategy are confirmed by theoretical analysis and computer simulation.

Published
2013

36. Production of triploid eastern little tuna, Euthynnus affinis (Cantor, 1849).

Author

Yazawa, Ryosuke, Machida, Yuri, Amezawa, Kotaro, Kabeya, Naoki, Tani, Reoto, Kawamura, Wataru, Yoshizaki, Goro, and Takeuchi, Yutaka

Subjects
AQUACULTURE, AGRICULTURE, ALGAE culture, FISH farming, CHROMOSOME abnormalities
Abstract

Herein, we developed a triploidization method using spawned eggs collected immediately after spawning of eastern little tuna (ELT), Euthynnus affinis. ELT broodstock induced the spawning by hormonal treatment in the tank, with the resulting spawned eggs being used for the triploidy induction. Under optimal conditions, the mean ± SEM triploidization and hatching rates were 97.2 ± 2.8% and 84.5 ± 10.3%, respectively. Although triploid ELT showed growth performance equivalent to that of diploids, the triploids died at a higher rate than the diploids during 2–4 weeks post‐hatching when triploids and diploids were reared in the same tank. Therefore, we propose that it would be necessary in a practical operation to use triploid‐only ELT seedlings to avoid selective cannibalism by the diploids. The ELT triploids exhibited an all‐female phenotype. Because previous studies have reported that female triploids show a greater probability of sterility than male triploids, this characteristic could be a major advantage. Since this triploidization method, using spawned eggs, can be performed without handling the broodstock, it is possible to avoid the physical damage caused by the process of artificial insemination, making it possible to repeatedly produce triploid populations without valuable broodstock loss. Thus, we have developed an efficient method to produce ELT triploids, although further study is essential to evaluate sterility of the triploid ELT. [ABSTRACT FROM AUTHOR]

Published
2019
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48. Density-tunable conjugation of cyclic RGD ligands with polyion complex vesicles for the neovascular imaging of orthotopic glioblastomas

Author

Kawamura, Wataru, primary, Miura, Yutaka, additional, Kokuryo, Daisuke, additional, Toh, Kazuko, additional, Yamada, Naoki, additional, Nomoto, Takahiro, additional, Matsumoto, Yu, additional, Sueyoshi, Daiki, additional, Liu, Xueying, additional, Aoki, Ichio, additional, Kano, Mitsunobu R, additional, Nishiyama, Nobuhiro, additional, Saga, Tsuneo, additional, Kishimura, Akihiro, additional, and Kataoka, Kazunori, additional

Published
2015
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