- 著者
- Yudai Funaki Keiji Wada
- 出版者
- The Institute of Electrical Engineers of Japan
- 雑誌
- IEEJ Journal of Industry Applications (ISSN:21871094)
- 巻号頁・発行日
- pp.22006323, (Released:2022-12-02)
- 被引用文献数
- 3
SiC devices are potential future power devices because of their higher switching speed and lower ON resistance than those of Si devices. Research and development efforts to apply them in medium- and large-capacity power conversion circuits are underway. However, SiC power devices in TO packages, which are general-purpose packages, are difficult to apply in high-current applications owing to their low current ratings. Therefore, increasing the capacity of power devices by connecting them in parallel is being studied. However, the current imbalance during switching due to the differences in device characteristics and variations in parasitic inductance is problem. This study proposed a current-balancing procedure focused on the parasitic inductances around power devices and gate drive circuit implementation. The proposed method was verified by conducting double-pulse tests at 300 V and 200 A.
- 著者
- Daisuke Numaguchi Keiji Wada Mitsuru Yui Ryo Tamaki Ken Okazaki
- 出版者
- The Japanese Society for Spine Surgery and Related Research
- 雑誌
- Spine Surgery and Related Research (ISSN:2432261X)
- 巻号頁・発行日
- vol.3, no.2, pp.141-145, 2019-04-27 (Released:2019-04-27)
- 参考文献数
- 19
- 被引用文献数
- 3 6
Introduction: The incidence of remote cerebellar hemorrhage (RCH) in patients with a dural tear during spinal surgery is unclear. The purpose of this study was to determine the incidence of RCH and the causative factors in these patients.Methods: Two hundred and thirty-nine patients underwent spinal surgery at our institution between March 2015 and September 2016. Eleven of these patients needed dural suturing intraoperatively. All patients underwent CT of the head on the first postoperative day and were categorized according to whether they had RCH or not. The mean values for the amount of intraoperative bleeding, maximum perioperative blood pressure, postoperative drainage volume, and complaints of headache during the first 24 h postoperatively were compared between the two groups using the Welch's two-sample t-test and Fisher's exact test. The follow-up duration was 12 months.Results: There were four patients in the RCH group and seven in the non-RCH group. The incidence of RCH was 36.4%. There were three cerebellar hemorrhages and one interhemispheric fissure hemorrhage in the RCH group. The mean intraoperative bleeding volume was 284 mL in the RCH group and 569 mL in the non-RCH group. The mean respective values for maximum perioperative blood pressure and postoperative drainage volume were 132 mmHg and 547 mL in the RCH group and 144 mmHg and 567 mL in the non-RCH group; none of the differences was statistically significant. However, complaints of headache in the first 24 h postoperatively were significantly more common in the RCH group than in the non-RCH group (100% vs. 14.3%; p = 0.01). All patients with intracranial bleeding had recovered 3 months after surgery.Conclusions: The incidence of RCH following a dural tear during spinal surgery was 36.4%. There was a significant association between RCH and increased reporting of headache during the first 24 h postoperatively.
- 著者
- Shotaro Takahashi Keiji Wada Hideki Ayano Satoshi Ogasawara Toshihisa Shimizu
- 出版者
- The Institute of Electrical Engineers of Japan
- 雑誌
- IEEJ Journal of Industry Applications (ISSN:21871094)
- 巻号頁・発行日
- pp.21006800, (Released:2021-08-13)
- 被引用文献数
- 11
The switching frequency of power converters is continuing to increase with the demand for their increased power density. Therefore, the frequency band of the electromagnetic interference (EMI) generated by power converters ranges from several kilohertz to 100 MHz or more, thereby increasing the importance of EMI countermeasures in power converters. In addition, with the practical applications of smart grids and microgrids and the introduction of 5G technology, cases wherein power converters and information communication devices are placed in close proximity are continuing to increase. Thus, in societies wherein power converters and information communication devices are highly integrated, it is necessary to ensure electromagnetic compatibility based on a different concept. This paper presents a review on modeling and suppression techniques for the EMI generated by power converters and discusses future prospects in this field.
- 著者
- Ryo Shirai Naoki Aoshima Keiji Wada
- 出版者
- The Institute of Electronics, Information and Communication Engineers
- 雑誌
- IEICE Communications Express (ISSN:21870136)
- 巻号頁・発行日
- vol.11, no.9, pp.566-570, 2022-09-01 (Released:2022-09-01)
- 参考文献数
- 7
This paper proposes a platform for electromagnetic interference on Ethernet communication devices due to conducted noise from power conversion circuits, focusing on the electromagnetic near-field coupling between the DC bus and the communication line. The waveforms measured on the platform during switching transients reveal the mechanism of communication failure. The Ethernet performance evaluation by a network protocol analyzer shows that the converter switching frequency impacts the communication error rate.
- 著者
- Kyosuke Shimo Keiji Wada
- 出版者
- The Institute of Electrical Engineers of Japan
- 雑誌
- IEEJ Journal of Industry Applications (ISSN:21871094)
- 巻号頁・発行日
- pp.22000978, (Released:2022-08-12)
- 被引用文献数
- 1
Magnetization reversal motors (MRMs) have been proposed as motors with lower power losses. MRMs comprise the same configuration as interior permanent magnet synchronous motors; however, a low coercive force core is applied to the stator. Driving an MRM requires a pulse current for magnetizing the stator core. In this paper, a bipolar pulse current magnetizer is proposed for driving MRMs Moreover, the relationship between passive components is reported in terms of voltage, current, and circuit constant. Finally, this paper presents experimental verification of the proposed magnetizer using an inductive load to simulate a single phase of an MRM.
- 著者
- Yasushi Hori Manami Fujisawa Kenji Shimada Akira Oda Shinichiro Katsuyama Keiji Wada
- 出版者
- The Pharmaceutical Society of Japan
- 雑誌
- Biological and Pharmaceutical Bulletin (ISSN:09186158)
- 巻号頁・発行日
- vol.27, no.4, pp.486-491, 2004 (Released:2004-04-01)
- 参考文献数
- 17
- 被引用文献数
- 11 32
We have established a new method of HPLC analysis for the rapid separation from human serum and the quantification of 4-O-methylpyridoxine (MPN), which is contained in Ginkgo biloba seeds, and which, when consumed in large amounts, causes vomiting and convulsions. As a result of using IPCC-MS3 (GL Science, Tokyo, Japan), an ion-pair reagent, in the mobile phase, we succeeded in separating MPN in the deproteinized serum sample which was introduced directly onto the reverse-phase HPLC column. For the calibration curve of MPN standard solution, prepared with fluorescence detection at an excitation wavelength of 290 nm and an emission wavelength of 400 nm, a good linear relationship was obtained within the HPLC injection range of 10 ng—10 pg (in terms of the injected sample concentration, range: 1.0 μg/ml—1 ng/ml), allowing the detection of minute amounts, with the limit of detection (concentration of injected sample: 500 pg/ml) being 5 pg. In addition, when MPN solution was added to human reference serum to give a concentration of 0.002 μg/ml, the mean recovery rate was 92.5%, with RSD=7.09% (n=5). The time required for one analysis using this method is approximately 30 min, and thus it offers the advantages of greater speed and superior analytical sensitivity over the conventional methods, which require solid-phase extraction. We employed our new method to determine both the serum levels of MPN in 5 patients with Ginkgo biloba seed poisoning and the levels of free-form MPN in such seeds obtained in 8 regions of Japan.
- 著者
- Keiji Wada Yukihisa Suzuki Akira Ushiyama Shin Ohtani Kenji Hattori Atsushi Saito Satoshi Nakasono Satoshi Miyawaki Takashi Yanagisawa Yoshiya Ohnuma
- 出版者
- The Institute of Electronics, Information and Communication Engineers
- 雑誌
- IEICE Communications Express (ISSN:21870136)
- 巻号頁・発行日
- vol.11, no.10, pp.661-666, 2022-10-01 (Released:2022-10-01)
- 参考文献数
- 7
This letter presents development of a magnetic field generator to evaluation of biological effects. The magnetic field generator has a frequency bandwidth of 85 kHz because it is intended for wireless power supply for electric vehicles. Furthermore, the generator is designed to operate for only one second, and can produce the induced magnetic field of 10 times compared to basic restrictions of the ICNIRP. By applying the magnetic field generator, it is possible to conduct a evaluation and verification of biological effect depending on electromagnetic fields for WPT systems of electric vehicles.
- 著者
- Shin-Ichiro Hayashi Keiji Wada
- 出版者
- The Institute of Electrical Engineers of Japan
- 雑誌
- IEEJ Journal of Industry Applications (ISSN:21871094)
- 巻号頁・発行日
- vol.11, no.1, pp.108-116, 2022-01-01 (Released:2022-01-01)
- 参考文献数
- 26
- 被引用文献数
- 7
This study presents a design method for the continuous switching test circuits of power devices. Depending on the relationship between the rated voltage of a DC voltage source and device under test (DUT), two types of test circuits are proposed. These test circuits comprise a cascaded buck-boost (or boost-buck) converter to achieve power regeneration. Based on analysis of the test circuits, a design method is proposed to ensure that any failure does not spread to the test circuit even when the DUT fails during the continuous switching tests. A test circuit is designed according to the proposed method, and its experimental results demonstrate the validity of the proposed design.
- 著者
- Shotaro Takahashi Keiji Wada Hideki Ayano Satoshi Ogasawara Toshihisa Shimizu
- 出版者
- The Institute of Electrical Engineers of Japan
- 雑誌
- IEEJ Journal of Industry Applications (ISSN:21871094)
- 巻号頁・発行日
- vol.11, no.1, pp.7-19, 2022-01-01 (Released:2022-01-01)
- 参考文献数
- 152
- 被引用文献数
- 11
The switching frequency of power converters is continuing to increase with the demand for their increased power density. Therefore, the frequency band of the electromagnetic interference (EMI) generated by power converters ranges from several kilohertz to 100MHz or more, thereby increasing the importance of EMI countermeasures in power converters. In addition, with the practical applications of smart grids and microgrids and the introduction of 5G technology, cases wherein power converters and information communication devices are placed in close proximity are continuing to increase. Thus, in societies wherein power converters and information communication devices are highly integrated, it is necessary to ensure electromagnetic compatibility based on a different concept. This paper presents a review on modeling and suppression techniques for the EMI generated by power converters and discusses future prospects in this field.
- 著者
- Van-Long Pham Keiji Wada
- 出版者
- The Institute of Electrical Engineers of Japan
- 雑誌
- IEEJ Journal of Industry Applications (ISSN:21871094)
- 巻号頁・発行日
- vol.9, no.3, pp.227-234, 2020-05-01 (Released:2020-05-01)
- 参考文献数
- 19
- 被引用文献数
- 4
This paper proposes a normalization design for series inductances in a triple active bridge (TAB) converter. The voltage variations and inductances are normalized based on percentage, and the complicated relationships between the elements of the TAB converter are clarified. The limitation of inductances corresponding to the different voltage variations is specified. The inductances are designed by considering the operation range of the phase shift angles. Based on this, the proposed method allows the inductances in TAB converter to be designed for various applications. A prototype converter rated at 200V and 500W is implemented to verify the proposed method. The experimental results show that the converter can operate under the rated power, indicating that the proposed method can be applied for designing of a TAB converter.
- 著者
- Seiji Iyasu Yuji Hayashi Yuichi Handa Kimikazu Nakamura Keiji Wada
- 出版者
- The Institute of Electrical Engineers of Japan
- 雑誌
- IEEJ Journal of Industry Applications (ISSN:21871094)
- 巻号頁・発行日
- vol.8, no.3, pp.437-443, 2019-05-01 (Released:2019-05-01)
- 参考文献数
- 14
- 被引用文献数
- 6
Electric vehicles are equipped with an isolated DC-DC converter for controlling the bidirectional DC power flow. In this case, a current sensor was installed inside the circuit. This paper proposes a current sensor using current transformers for bidirectional DC-DC converters. The current sensor comprises a current transformer (CT), diode rectifier, and MOSFET. The current sensor can detect a pulse current containing a DC component without any magnetic saturation. This paper shows a circuit configuration of the bidirectional current sensor, and the principle of the bidirectional current detection of the sensor is analyzed. The validity of this analysis is verified through an experiment with the DC-DC converter rated at 150V and 1.4kW.