Norikazu Tokunaga
Hitachi
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Featured researches published by Norikazu Tokunaga.
power electronics specialists conference | 1988
Ikuo Yamato; Norikazu Tokunaga; Yasuo Matsuda; Hisao Amano; Yutaka Suzuki
A novel conversion system for a UPS (uninterruptible power supply) using a high-frequency link is described. The UPS consists of a high-frequency inverter and transformer and a cycloconverter. The cycloconverter can be operated by both source commutation and self-commutation (by turning off the switching devices). A choice is made between the two commutation methods, depending on switching device losses during commutation and the internal voltage drop caused by commutating reactance. A compact and efficient UPS can be realized with this conversion system.<<ETX>>
power electronics specialists conference | 1990
Ikuo Yamato; Norikazu Tokunaga; Yasuo Matsuda; Yutaka Suzuki; H. Amaro
A power conversion system for a UPS (uninterruptible power supply) using a high-frequency link is described. The proposed UPS consists of a high-frequency inverter, a high-frequency transformer, and a cycloconverter with a new voltage clamper. The clamper effectively reduces the power loss of the conversion system. The voltage clamper gave an improved DC-AC conversion efficiency of about 10% more than when a conventional RC snubber was used. When source-commutation was used, DC-AC conversion efficiency was improved by about 5%. When the voltage clamper was used both DC-AC conversion efficiency and the output voltage characteristic without the automatic voltage regulator were improved to source commutation. Fabrication of a 10 kVA high-frequency-link DC-AC power converter is described and its loss reduction effect is demonstrated.<<ETX>>
power electronics specialists conference | 1993
Ikuo Yamato; Norikazu Tokunaga
A three phase high frequency link DC-AC power converter suitable for UPS (uninterruptible power system) applications is described. This converter consists of a high frequency inverter, a high frequency transformer, and a cycloconverter. Power loss reduction techniques for the cycloconverter are discussed, which include zero voltage switching, source commutation, and a voltage clamper. Fabrication of a 3 kVA high frequency link DC-AC power converter is described and its loss reduction effect is demonstrated.<<ETX>>
Archive | 1990
Hideki Miyazaki; Ikuo Yamato; Kenichi Onda; Yasuo Matsuda; Yuzo Morita; Hidefumi Shirahama; Norikazu Tokunaga; Yutaka Suzuki
Archive | 2002
Norikazu Tokunaga; Kenichi Onda; Takeshi Onaka; Satoru Masuyama; Ryouhei Saga; Katsunori Hayashi
Archive | 2004
Nobuyuki Aihara; Takeshi Onaka; Norikazu Tokunaga; Kenichi Onda; Satoru Masuyama; Shigekazu Zemba
Archive | 2000
Kenji Kubo; Takahiro Nomura; Norikazu Tokunaga; Hideki Miyazaki; Akihiko Emori
Archive | 1993
Hidefumi Shirahama; Yorito Jifuku; Akira Kobayashi; Keizo Shimada; Norikazu Tokunaga; Yoshimi Sakurai; Ikuo Yamato; Tomoaki Mino; Satoru Inukai
Archive | 1991
Ikuo Yamato; Norikazu Tokunaga
Archive | 1984
Norikazu Tokunaga; Hiroshi Fukui; Kouzou Watanabe; Hisao Amano; Masayoshi Sato
