bluuebunny/crossref_metadata_2025_split huggingface dataset:
A high‐sensitivity magnetic field sensor shielded from the effect of earth's magnetism
Authors: Sonoda Toshikatsu , Ueda Ryuzo , Ikemoto Hajime 
Published: July 2007

AbstractTo realize a general‐purpose magnetic field sensor having a detection sensitivity of the order of 10−12 T/Hz at room temperature, a problem of removing the effect of the Earth's magnetism from the sensor must be solved because its magnitude is 4.5 × 104 times larger than that in the range to be detectable. For this purpose, a well‐known approach of exciting the sensor in the opposite direction to the Earth's magnetism to cancel out the value has been adopted.This paper aims at realizing a magnetic field sensor free from the Earth's magnetism by introducing a method called “zero magnetic field.” In practice, such a sensor was developed and the tested results confirmed that the detection performance was maintained without losing the high sensitivity.
Development of a large‐capacity static var generator using self‐cornmutated inverters for improving power transmission system stability
Authors: Hasegawa Taizo , Betsui Takashi , Ohnishi Shuichi , Takeda Masatoshi , Seto Makoto , Murakami Shotaro , Kohan Toyokazu 
Published: July 2007

AbstractA Static Var Generator (SVG) based on a self‐commutated inverter using GTO thyristors has been newly developed. The size of the SVG used for improving power system stability will be as large as approximately 100 MVA. The technical subjects to be solved for developing such a large SVG are summarized as follows:
compact design;
harmonic elimination by means of multiple transformers; and
large inverter with series connection of GTO thyristors.
This paper describes the solutions to these subjects, especially the application of a large number of multipulse connection and series connection of GTO thyristors, including the analysis of the basic performance of SVG and the multiple transformer. The test results of a 12‐pulse partial model (8 MVA) and a 48‐pulse miniaturized model prove the solutions proposed in this paper to be effective and reasonable.
MRAS‐based speed sensorless control scheme with stator resistance identification function for vector‐controlled induction motor drives
Authors: Yang Geng , Chin Tung‐Hai 
Published: July 2007

AbstractThis paper describes a new scheme for the speed sensorless control of the vector‐controlled induction motor drive.Based on the model reference adaptive system (MRAS) theory, the rotor speed of the induction machine is estimated with a full‐order adaptive observer. The estimated speed then is used as the signal for the vector control and the speed control. To accurately estimate the speed at the lower speed range, the value of the stator resistance also is identified at the same time and then is used to modify the resistance value set in the observer. The resulting system is verified to be hyperstable with Popov's criterion. As a result, this drive can operate stably in a wide range of speed even at zero speed. Also, it is shown theoretically that neither speed nor resistance of the rotor can be identified at the same time because these two parameters are dependent on each other. Simulation results and experiments also show that the scheme is effective.
Hyperstability of the full‐order observer for vector‐controlled induction motor drive without speed sensor
Authors: Yang Geng , Chin Tung‐Hai 
Published: July 2007

AbstractVector‐controlled induction motor drive systems without speed sensors have been widely studied. Speed estimation can be treated as a problem of parameter estimation under the theory of MRAS (model reference adaptive systems). In such cases, the convergence and robustness of the system are major issues. In this paper, we discuss the stability of an MRAS, that includes a full‐order adaptive observer of the induction motor and is used for estimating the rotor speed and identifying the stator resistance. It is verified that, under some conditions, the transfer matrix in the forward path of the MRAS is strictly positive‐real and that the non‐linear block in the feedback path satisfies Popov's criterion. As a result, the system is hyperstable. The influence of the set error of the rotor resistance is discussed and the design criterion for the feedback gain of the observer is presented. Finally, the system is linearized for the parameter design of the speed estimator.
Prospects for the application of superconductivity technology to power systems
Authors: Hashimoto Yasuo , Ito Shunichi , Hasegawa Taizo , Mino Yoshiaki 
Published: July 2007

AbstractBy relying only on the conventional technology, it may be difficult to meet the recent requirements of electric power systems such as further improvement of the quality of electric power supply, environmental compatibility, and so on. Some of the limitations of conventional technology can be eliminated by the application of superconductivity technology. Roughly speaking, superconductivity‐applied components which have relatively high feasibility are the superconducting generator, small‐capacity SMES. and liquid nitrogen‐cooled superconducting cable. To use them practically, reliability, maintainability, controllability and economy must be improved to the level of conventional components.
Contact‐failure phenomena and their development in gas‐insulated switchgear
Authors: Mukaiyama Yoku , Takagi Isao , Izumi Kunikazu , Sekiguchi Terukazu , Kobayashi Akio , Sumikawa Toshio 
Published: July 2007

AbstractTo explain contact failure phenomena and their development in the gas‐insulated switchgear (GIS). tests were conducted by simulating abnormal current‐carrying conditions using an actual 300‐kV, 2000‐A GIS.This paper describes the process observed. ranging from contact failures to ground faults, deteriorative phenomena and some detection methods for initial contact failure conditions. A summary of this study is as follows:(1) The contact resistances are greatly dependent on the materials and construction of contacts.(2) The relation between the initial contact resistance and the carried current resulting in arcing is derived with approximately constant Joule‐heat generation.(3) Ground faults result from sagging of a shield melted by arcing or a combination of two causes: (i) scattering of molten metal caused by arcing; and (ii) sagging of a conductor caused by bolt melt down.(4) To detect initial contact failures, it is recommended to observe the contact resistance, the temperature rise on the tank surface, or the electrical partial discharges.
Cooling characteristics of a large‐current capacity AC superconducting cable
Authors: Torii Shinji , Akita Shirabe , Tsukamoto Osami 
Published: July 2007

AbstractDiameter of the superconducting ac composite strand is small, typically 0.1 mm, because the strand must be twisted in a very short pitch to reduce coupling losses. Therefore, current capacity of the single strand is small and in the range of ∼10 A. In large‐scale electric power apparatus, the conductors must be able to carry large currents and hundreds of these composite strands should be bundled. The composite strand is highly unstable and susceptible to a very small disturbance due to a frictional wire motion because the main matrix of the wire is highly resistive CuNi.For stable operation of an ac superconducting winding, every strand in the bundle cable should be fixed firmly. An effective technique to fix strands is to impregnate the winding by epoxy. In this case, the ac losses in the winding are to be cooled by heat conduction through the epoxy. Therefore, it is important to estimate the temperature rise of the winding to discuss the fact that the epoxy impregnation technique is applicable to the ac superconducting electric power apparatus.In this paper, the mechanism of thermal conduction of the epoxy‐impregnated winding at the 4.2 K region is discussed based on experimental data and the temperature rise of a large‐scale cable bundles by 7 × 7 × 7 strands calculated considering thermal resistivity at the interface between the epoxy and the strand. The calculated value agrees well with the measured value.
A new partial discharge detection method for live UHV/EHV cable joints
Authors: Fukunaga Kaori 
Published: July 2007

AbstractPartial discharge (PD) detection on live UHVEHV power cables and accessories is one of the most important techniques to prevent cable systems from serious difficulties caused by slight errors in joining the cables. A new PD detecting method is proposed in this paper. A resonance‐type partial discharge (REDI) sensor is developed for detecting PD occurring inside the joints of live XLPE insulated cables. This sensor picks up the high‐frequency components of PD current pulses on the surface of live cables, hence the output signals can clearly be observed at the noiseless area (for example, 10‐60 MHZ).This new method was applied to the initial ac breakdown tests with three different types of joints of UHV/EHV power cables. The PD pulse sequence was detected before their breakdown in all cases. The charge quantity and the number of pulses increased tremendously just before the breakdown. In addition, the phase of PD pulse against the applied voltage (ϕ‐q characteristics) changes with time or with the progress of deterioration. According to these experimental results, the REDI sensor can be applied to the insulation diagnosis of live power cable joints.
Basic characteristics of a self‐excited induction generator under secondary excitation at constant voltage
Authors: Koyakumaru Yoshinori , Miyanaga Hiroaki 
Published: July 2007

AbstractA self‐excited wound‐rotor induction generator excited with a capacitor can be used as an independent source for small‐capacity wind power generator.With constant excitation capacitance, the secondary‐circuit power of the induction generator is returned to the primary circuit through a converter, an inverter and a transformer; the power is controlled at the inverter so that the generator voltage is always maintained constant in spite of the changes of generator speed and load. The basic characteristics of the generator under the above conditions are analyzed.The fundamental waves of both the main circuit and the feedback circuit are determined. Using these results, the equations for various portions of the generator are derived, the performance characteristics of the generator are then analyzed and compared with experimental results.
Quench propagation of forced‐flow‐cooled superconducting coil
Authors: Shimada Mamoru , Hamajima Takataro , Yamaguchi Mitsugi 
Published: July 2007

AbstractForced‐flow‐cooled superconducting coil (FCC) has several advantages: large stability margin; high mechanical rigidity; and good electrical insulation. As a result, FCC could provide efficient superconducting magnet systems for such large machines as fusion devices.Cable‐in‐conduit conductor (CICC) is regarded to be most attractive for FCC because of its good heat transfer characteristics which make the magnet more stable against disturbances. However, there are some problems. One problem is that the coolant pressure will become very high during a quench because its hydraulic diameter is relatively small. Also. the propagation of a normal zone has a close relation with the pressure rise. These characteristics must be considered in designing and protecting FCC.This paper describes the results of the stability tests of FCC and the analyses of these characteristics. and compares them with the results of numerical simulations.
Measurement of the magnetic characteristics of oriented silicon steel in an arbitrary direction
Authors: Morino Harumi , Ishihara Yoshiyuki , Todaka Toshiyuki 
Published: July 2007

AbstractThe measurement method and the experimental results on the magnetic characteristics of oriented silicon steel in any direction are described in this paper. A single sheet tester of rotational loss has been used in order to simulate conditions existing in real devices. The flux of any direction is induced in the specimen by exciting from X and Y directions in the same phase. The flux density was measured by each search coil. The magnetizing force was measured by the double H‐coil method. The outputs of the B‐coils and the H‐coils were treated by sending the outputs from the wave digitizer to the personal computer.The components of the magnetic characteristics in the X and Y directions for small values of B are the same. Only the saturation value changes, and it depends on the direction of flux.
Suppressing the effect of lightning‐induced overvoltages by the combined use of surge arresters and overhead ground wires
Authors: Morooka Yasunari , Yokoyama Shigeru , Asakawa Akira 
Published: July 2007

AbstractLightning voltage induced by nearby strokes is one of the causes of major overvoltages which threaten the insulation of power distribution lines. Surge arresters as well as an overhead ground wire usually are employed for the protection of equipment and line insulation on overhead power distribution lines.The fundamental mechanism of suppressing effects of overvoltages induced by nearby strokes has been demonstrated independently by one of the present authors for surge arresters and for an overhead ground wire.In this paper, the protective effect of the combination of surge arresters and overhead ground wire is analyzed. As a result, it is found that the effect of surge arresters used together with an overhead ground wire is almost the same as that of surge arresters alone.
Optimal pulse patterns of a nine‐phase voltage source PWM inverter for use with a triple three‐phase wound ac motor
Authors: Takami Hiroshi , Matsumoto Hisao 
Published: July 2007

AbstractThe authors have already described the nine‐phase inverter driving system providing both the triple three‐phase voltage source inverter with 180‐deg conducting period and the ac motor windings with triple three‐phase construction. The nine‐pulse inverter driving system used three small‐capacity three‐phase coupling reactors having special windings for current balance and reduction of higher harmonics.In addition, for voltage control, current balance, and waveform improvement, optimal PWM pulse patterns were applied to the six‐phase inverter driving system using a three‐phase coupling reactor to provide double three‐phase construction.In the system based on the mode in the title, the PWM control was applied to the nine‐phase inverter driving system described in the foregoing. The coupling reactors in the system balance the fundamental currents of three sets of three‐phase inverters and also absorb higher harmonic voltages other than 18p±1 (p = 1, 2, …) orders. The optimal pulse patterns found by the approach to make the performance index minimum using the Lagrange multiplier method can be applied to the PWM to reduce the higher harmonic currents greater than those calculated by the modulation method comparing the sinusoidal signal wave with triangular carrier signal.This system can have a larger capacity than the six‐phase PWM inverter driving system in which coupling reactors absorb higher harmonic voltages other than the 12p±1 orders and also improve output current waveforms. In addition, the system includes the capacity of coupling reactors slightly larger than the six‐phase PWM inverter driving system but enables operation with smaller torque ripples and electromagnetic noises in low‐ to high‐frequency ranges.
Static thrust analysis of a cylindrical moving‐core linear oscillatory actuator
Authors: Yamaguchi Masaki , Nagumo Masamichi , Iio Minoru , Yamada Hajime , Mizuno Tsutomu , Suzuki Hiroya 
Published: July 2007

AbstractThis paper considers materials for the movers, the volume ratio of the stator and of the mover, and the structure of the mover in a cylindrical moving iron‐type linear oscillatory actuator (LOA) having a permanent magnet. As a result, we obtain the following:

the static thrust characteristics are evaluated on two movers: movers P and S are made of a permendur and a stainless steel, respectively. It is clarified that the static thrust of the mover P is 30 percent larger than that of the mover S;
it is suggested that the structure of the mover P should be improved to eliminate a “lump” in the static thrust‐displacement curve due to the step on the mover, and which disturbs the smooth motion of the LOA.
An automatic torque ripple compensation system for direct drive motors
Authors: Sato Hirokazu , Makino Tatsuo , Matsui Nobuyuki 
Published: July 2007

AbstractA serious problem in motion control is the occurrence of torque ripple. Since a direct drive (DD) motor with a magnet rotor uses a rare‐earth magnet, the torque ripple is more serious than that of conventional servomotors.This paper presents an auto‐compensation of torque ripple using a software‐implemented torque observer. The frequency and amplitude of torque ripple can be obtained in the controller by using the estimated torque from an observer, and the autonomous generation of a compensating current component for a torque ripple is possible. The proposed algorithm has been verified by experiments.
Flashover characteristics of vapor‐mist dielectrics under lightning impulse and means to increase the flashover voltage
Authors: Yashima Masafumi , Fujinami Hideo , Takuma Tadasu 
Published: July 2007

AbstractIt has been reported that the flashover voltage of gaseous dielectrics may increase greatly when they are mixed with carbon‐halide mist. However, the factors which bring about the increase of the flashover voltage still are not clarified fully. Based on the study on the basic flashover characteristics of vapor‐mist dielectrics, the authors have suggested the scarcity of initial electrons as the predominant factor.This paper investigates further the effect of UV light irradiation, flashover characteristics under forced supply of initial electrons, and for lightning impulse superimposed on dc voltage. These results have verified that the scarcity of initial electrons is the decisive factor in increasing the lightning impulse flashover voltage of vapor‐mist dielectrics. It is clarified also that the scarcity is attributed principally to: (1) the reduction of effective period (lifetime) of initial electrons, and (2) the suppression of photoelectric emission from electrodes.
New digital control and protection equipment using multiprocessor architecture of distributed functions for power system
Authors: Chiba Tomio , Kido Mitsuyasu , Kawakami Junzo , Kudo Hiroyuki , Kawai Tadao 
Published: July 2007

AbstractControl and protection of equipment in power systems generally require a high‐information processing capability to cope with today's power system requirements. Then, new digital control and protection equipment have been developed using high‐speed and high‐precision processors.Essential requirements for the new control and protection equipment are a multiprocessor architecture of distributed functions to retain sufficient computing power (fast and high‐precision operations), and flexible and expandable hardware with high reliability. In multiprocessor architecture, it is important to determine how the distributed processors share the functions. By analysis and synthesis of relaying and control processings, we divided them into six processing circuits.This paper proposes a multiprocessor architecture of distributed functions, using 32‐bit floating‐point and 16‐bit microprocessors depending on the computational requirements. In addition a digital filter for fast sampled data is described along with performance of a digital relay.
Development of the double‐rod‐type jumper horns in strain assemblies with pipe jumpers for 500‐kv transmission lines
Authors: Shibuya Masatoyo , Amakawa Tadashi , Sano Kiyoshi , Kimura Sakae 
Published: July 2007

AbstractThis paper proposes double‐rod‐type jumper horns in strain assemblies with pipe jumpers for 500‐kV transmission lines, the structure of which is very simple. It can be estimated that no corona discharge appears on the horns under the line voltage of 525 kV. The arc behavior on the double‐rod‐type jumper horns is similar to that on the single‐rod‐type horns. The arc can be held stably for 60 ms against strong wind (10 m/s). The stable duration increases more than 300 ms under windless condition, therefore the horns have been adopted for practical use.
Superconducting compact synchrotron light source
Authors: Takada Hiroshi , Tsutsui Yasumitsu , Emura Katsuji , Tomimasu Takio 
Published: July 2007

AbstractA superconducting compact synchrotron light source, the NIJI‐III, has been completed. The development of the NIJI‐III was assigned to Sumitomo Electric Industries Ltd. by the Research Development Corporation of Japan and was deemed successful in October 1991 with the attainment of the design goal of the stored beam current of 200 mA at the final beam energy of 600 MeV. The lattice has a four‐sector configuration: four superconducting bending magnets and eight quadrupole magnets, achieving the optimum beam characteristics for lithography. The world's first superconducting bending magnet was developed and adapted, and was characterized by a cosθ type without an iron, a large bore of 200 mm, and a strong curvature of 0.5 m. Furthermore, a newly developed vacuum system and an rf system were installed.The high‐speed electron‐beam wobbling method was investigated at a 20‐Hz triangular wave for the exposure of the vertical field of synchrotron light. It was demonstrated that the expansion of the vertical exposure area agreed with the theoretical calculation, and that there was no effect on the beam lifetime.The achievement of the NIJI‐III can be expected to contribute much to the development of various research applications of synchrotron light.
Analysis of brushless three‐phase synchronous generator without exciter
Authors: Nonaka Sakutaro , Kesamaru Katsumi , Horita Kazuo 
Published: July 2007

AbstractRecently, a demand for small‐capacity generators has been increasing as electric sources in small ships and automobiles or as portable electric sources driven by engines.It is desired that the structure of small‐capacity generators be simple and robust, and that the generators be highly reliable, easily maintained and controlled.This paper describes an analysis of the original brushless synchronous generator without exciter. The output voltage can be adjusted in the wide range by controlling the stator dc current. To analyze the characteristics of this generator, the finite element method is applied. It is found that the results of theoretical analysis agree well with the experimental results.
Flashover voltage characteristics of contaminated station insulators under temporary ac overvoltages in the ac system connected with a frequency converter station
Authors: Yamazaki Takashi , Takino Yoichi , Matsuoka Ryosuke , Ito Susumu 
Published: July 2007

AbstractAccording to the recent analysis results of temporary ac overvoltage in the ac system connected with a frequency converter station, large‐magnitude over‐voltages were confirmed to occur under some special system conditions.Most of the station insulators currently used cannot withstand such overvoltages according to an evaluation based on the data obtained earlier.The necessity of tests to be done to evaluate such performance more accurately was recognized. Both power frequency and switching impulse overvoltage flashover tests were made on contaminated insulators by the method well simulating the natural wetting condition.Switching impulse flashover voltage with the waveshape having a long wavefront time of 2 ms can be well correlated with the flashover voltage characteristics of temporary ac overvoltage. Higher flashover voltage characteristics were obtained by a clean fog test method compared with those obtained by equivalent fog test method.