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Diagnosis Criterion of Abnormality of Transformer Winding by Frequency Response Analysis (FRA) 下载免费PDF全文
SATORU MIYAZAKI YOSHINOBU MIZUTANI AKIRA TAGUCHI JUNICHI MURAKAMI NAOKAZU TSUJI MASAHIRO TAKASHIMA OSAMU KATO 《Electrical Engineering in Japan》2017,201(3):25-34
Frequency response analysis (FRA) is a powerful technique to detect internal abnormalities within power transformers. However, diagnosis criteria of power transformers by FRA have not been fully established yet. In this paper, a new evaluation method of degree of identification between two transfer functions is proposed. In the proposed method, a frequency window is employed and cross‐correlation factor is calculated with moving the window. Furthermore, the proposed method is applied to transfer functions of real transformers with or without some abnormalities. Based on this discussion, objective criteria for diagnosis of abnormalities of transformer windings by FRA are proposed. The proposed criteria are based on a few data of transformers with some abnormalities. Therefore, the proposed criteria are tentative and they would be improved by accumulation of further data. 相似文献
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YOSHIKI SUZUKI MINORU MIZUTANI TAKAMITSU SUGIURA NAOKI SAKAI TAKASHI OHIRA 《Electrical Engineering in Japan》2016,195(1):63-71
Electric vehicles (EVs) are expected to play a leading role in the changeover from fossil fuels to clean energy. However, EVs are currently not very popular, owing to their short cruising distance and long charging time. Wireless power transfer from the infrastructure to running EVs is expected to be the solution to these problems. Electric vehicle and electrified roadway (EVER) has been proposed as a wireless power transfer system for EVs while in motion. Via‐wheel power transfer (V‐WPT) is expected to be a wireless power transfer scheme for EVER. We designed and prototyped a 1:32 scale model of a V‐WPT system that consists of an RF inverter, an electrified roadway, a rectifier, and an EV with a dc motor. The output power of the prototype RF inverter was 5.9 W and the dc–RF conversion efficiency was 36.6%. The LC matching circuits for the V‐WPT were designed with two‐port conjugate matching because S11 of the V‐WPT was intrinsically –0.06 dB. After matching, the S11 value was reduced to –21.5 dB. The power transmission efficiency of the V‐WPT system was 75%. The RF–dc conversion efficiency of the rectifier was 62%. The total efficiency of the EVER system was 24.2%. 相似文献
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A Five‐Element Multiplex Resonant Full‐Bridge DC‐DC Converter with a Variable Inductive Reactance 下载免费PDF全文
A five‐element multiplex resonant (LLCLC) full‐bridge DC‐DC converter controlled by pulse frequency modulation (PFM) is proposed in this paper. The high frequency (HF)‐link resonant DC‐DC converter proposed herein can perform wide‐range output power and voltage regulation with a narrow frequency range due to an antiresonant tank that works effectively as a wide‐range variable inductor. The advantageous characteristics of the antiresonant tank provide overcurrent protection in the case of the short‐circuited load condition as well as in the startup interval. Thus, the technical challenges of a conventional LLC DC‐DC converter can be overcome, and the reliability of the relevant switch‐mode power supplies can be improved. The operating principle of the LLCLC DC‐DC converter is described, after which its performance is evaluated in an experimental setup based on the 2.5 kW prototype. Finally, the feasibility of the proposed DC‐DC converter is discussed from a practical point of view. 相似文献
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Influence of Drying Methods on Volatile Sulfur Constituents of Caucas (Allium victorialis L.) 总被引:1,自引:0,他引:1
C. HANNY WIJAYA HIROYUKI NISHIMURA TSUNEO TANAKA JUNYA MIZUTANI 《Journal of food science》1991,56(1):72-75
The effects of freeze-drying, hot air, and vacuum far infrared-drying on caucas (Allium victorialis L.) flavor was studied. The GC and GC-MS characterization of volatiles from dried caucas powders revealed the main flavor components; disulfides and trisulfides, as well as the antithrombotic substances; vinyldithiins, remained in all products. Vi-nyldithiins were isolated and subsequently confirmed by IR, NMR and Mass Spectrometry. Rehydration of the dried powders increased measurable volatile compounds, which were produced enzymatically. Increased-storage time decreased measurable volatiles in freeze-dried and hot air-dried caucas powders while the volatile profile remained unchanged. 相似文献
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ABSTRACT: Hydroperoxides and n -hexanal of soymilk made at different temperatures in the soybean grinding process were investigated. Both hydroperoxides and n -hexanal showed maximum amounts at 30°C, 37.78 μmol/g, and 1.94 mg/g, respectively. However, at 3°C and 80°C, amounts of hydroperoxides were about half of that at 30°C. N -hexanal showed high correlation with hydroperoxides except for at 80°C. It suggests that controlling the grinding temperature is effective to reduce hydroperoxidation and off-flavor content. Protein solubility an important index of soymilk, was decreased as the temperature increased. Grinding soybeans at low temperature is considered an economical method to produce soymilk having less off-flavor and high protein. 相似文献
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Physical State of the Dispersed Phases of Emulsions Prepared with Egg Yolk Low Density Lipoprotein and Bovine Serum Albumin 总被引:1,自引:0,他引:1
Physical state of the dispersed phases of the emulsion prepared with egg yolk low density lipoprotein (LDL-emulsion) was compared with that of bovine serum albumin (BSA-emulsion). Results clearly showed that the mean globule size of LDL-emulsion was much smaller than that of BSA-emulsion and that stability of the LDL-emulsion during storage was much larger than the BSA-emulsion. These properties of LDL-emulsion appeared to be dependent on the high lipid-binding ability of LDL. 相似文献
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A square plate resonator of contour mode is described in a low frequency operation. The resonator has four-part arched interdigital electrodes (IDEs) on one surface of a piezoelectric ceramic plate. The IDEs are used both for the poling treatment and the excitation of the vibration. Three modes are excited according to the combination of polarization for driving the IDEs, which are the antisymmetrical-antisymmetrical (AA) mode, the antisymmetrical-symmetrical mode (AS), and the symmetrical-symmetrical (SS) mode. The AA mode resonator is obtained in a single mode operation around 256 kHz under a condition for mechanical support. 相似文献
10.
KENJI HIRAMOTO HIDEO NAKAI YUKO KANO EIJI YAMADA RYOJI MIZUTANI 《Electrical Engineering in Japan》2017,198(2):81-88
This paper presents a new type of magnet‐free motor that has concentrated stator windings and rotor coils with a pair of diodes. The most important feature of this motor is that currents in the rotor coils can be generated by utilizing the changes in the spatial second harmonic of the magnetic fields due to the concentrated stator windings, which normally increase motor losses. A prototype of the motor was designed and fabricated, and its basic performance was evaluated. First, using simplified analytic models, we explain the mechanism of inducing currents in the rotor coils by the changes in the spatial second harmonic of the magnetic fields. Second, we compare the torque performance of the proposed motor and that of other types of motors including a magnet motor through finite‐element analyses. The analyzed data show that the proposed motor can possess greater torque/volume ratio than that of the other motors. Finally, using the measured data, we validate the mechanism of inducing currents in the rotor coils, and examine the torque and power characteristics of the motor. 相似文献