bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adaptive control‐based high‐performance drive system implementation of traveling‐wave‐type ultrasonic motor
Authors: Izuno Yuji , Nakaoka Mutsuo 
Published: July 2007

AbstractIn recent years, ultrasonic motors (USM) as new actuators have attracted special interest. Several kinds of constructions and characteristics of USMs have been reported so far. Of these USMs, a traveling wave‐type USM has many characteristics such as: high torque in the low‐speed range, large holding torque based upon frictional force, flexible free forms, compactness in size and low magnetic noise. In practice, an inherent mechanical resonant frequency and a velocity amplitude of USM are changed largely according to operating temperature due to frictional drive, load disturbance torque, and applied voltage levels. Therefore, it is necessary to develop a new control system which solves these items and always supplies the required power with high efficiency and high performance in the practical applications.This paper proposes mainly a new sensorless high‐performance control scheme of an inverter‐fed ultrasonic motor, which is based on a control system technology with two feedbacks incorporating automatic resonant frequency tracking and constant velocity amplitude control strategies. This control system is realized in terms of a high‐frequency chopper and a two‐phase series/parallel resonant inverter. The experimental results are demonstrated and discussed compared with the theoretical ones.
66/77‐kV C‐GIS using composite insulation in SF6 gas
Authors: Masaki Nobuo , Yoshida Tetsuo , Miyagawa Masaru , Ohshima Iawo , Matsuzawa Kikuo 
Published: July 2007

AbstractA second‐generation model of cubicletype gas‐insulated switchgear (C‐GIS) with composite insulation incorporating SF6 gas has been developed. The design does not require a gas process in field assembly; it has high reliability and its installation is more rapid; and a further reduction in size is achieved. The design principles are described in detail.
A new calculation method of voltage rise of transmission towers and transmission lines by lightning stroke and calculated results
Authors: Motoyama Hideki , Matsubara Hiroji 
Published: July 2007

AbstractNew formulas for the surge impedances of transmission towers and transmission lines in lightning surge are derived. A comparison of results calculated by the proposed formulas with the experimental results show nearly the same wave crest values and wave‐forms. It is demonstrated that a large portion of the input current flows into the tower and only a small current flows into the ground wires. This fact is very important in investigating lightning performance in transmission towers and transmission lines. The results will be helpful in developing improved modes of transmission system performance.
Recognition of partial discharge pattern of electrode voids by neural network
Authors: Yanagisawa Takashi , Iwamoto Shinichi , Okamoto Tatsuki , Fukagawa Hiromasa 
Published: July 2007

AbstractA back‐propagation neural network model is used to identify electrode types involved in partial discharge (tree, IEC (b), CIGRE method I) and to estimate the shapes of the cylindrical electrode voids, based on the specific charge‐phase characteristics of the different electrode types.
Approximate method for calculating the impedances of multiconductors with cross sections of arbitrary shapes
Authors: Ametani Akirhiro , Fuse Ikuko 
Published: July 2007

AbstractThis paper proposes an approximate impedance formula of a conductor with an arbitrary cross section, and also a method of approximating the conductor by an equivalent circular conductor. Thus, a multiconductor system consisting of arbitrary cross section conductors is represented by circular cross section conductors, the impedance of admittance of which are evaluated by the existing impedance and admittance formulas.The calculated results by the proposed method agree satisfactorily with measured results and numerical results by a finite‐element method which is, at present, the only way of calculating such impedance, but requires a large computation time and large memory. The proposed method might be very useful in evaluating the impedance and admittance of a multiconductor system consisting of arbitrary cross section conductors.
A VAR planning method with multiple power‐flow states
Authors: Aoki Kenichi , Nishikori Akimine , Fan Mingtian , Satoh Taiji , Nara Koichi 
Published: July 2007

AbstractThe goal of reactive power (VAR) planning is to find the minimum cost installation plan of new reactive power sources so that the system voltage is maintained within an acceptable level. The consideration of multiple contingency states, together with the discrete nature of VAR facilities, creates a large‐scale nonlinear mixed‐integer programming (MIP) problem.To overcome the discrete nature of VAR facilities, an approximate method for the MIP problem is employed since the method is linear‐programming based and thus efficient for large‐scale problems. To treat the multiple contingencies, a resource directive decomposition approach is used in the proposed algorithm. If the number of installed VAR sources is fixed, the overall problem can be reduced to independent subproblems. Then subproblems are coordinated to give a VAR installation pattern in which installation cost becomes less than before. The algorithm proposed is tested for a 135‐node real‐size system and the results show the validity and effectiveness of the algorithm.
Control of magnetic bearing using the observer for unbalance
Authors: Mizuno Takeshi , Higuchi Toshiro 
Published: July 2007

AbstractAn unbalance on a rotor causes whirling motions of the rotor and alternating forces of the bearings in rotating machines. The authors have shown a magnetic bearing control system in which an unbalanced rotor can be suspended without whirling. The concept of designing the control system involved an observer estimating the effects of unbalance and then cancelling using the electromagnetic forces of the bearing.With the control method applied, the position of the rotor can be maintained at the desired position with high precision. However, it is suitable for some machines to minimize the variation of exciting currents or vibratory force transmitted to the base through the bearing.This paper presents control methods that can eliminate stationary alternating components from exciting currents or electromagnetic forces by using the output of the observer.Another control method is presented in which feedback of the estimated signals of the displacements of the principal axis occurs; such signals are obtained by compensating synchronous observatory disturbances by use of the output of the observer. It is shown that the proposed three control methods are equivalent when unbalance stiffness due to the bias magnetic flux is null.
A case‐based construction method for a fault‐restoration support system in secondary power systems
Authors: Okuda Kenzo , Nakagawa Kazumitsu , Yamazaki Katsuhiro 
Published: July 2007

AbstractThe authors have already clarified that case‐based reasoning (CBR) is very useful for the fault‐restoration support system in electrical power networks. This paper describes the case‐based construction method, adaptation and modification method of a case which is a fundamental process of CBR, and the results of evaluation.The following points were clarified through the simulations of fault restoration under various conditions with electrical power networks of practical scale: (1) a case‐based construction method and the guide to the selection of cases which should be included in the case were made clear. Restoration plans which include many cases are registered in the base. Cases which would require long computation time are also registered in the case base. In the application which requires high‐speed processing, such as fault restoration, there exists an optimum value in the total numbers of cases in the case base; (2) the function of load switching which is essential to perform adaptation and modification of a case flexibly was studied and embedded in the system herein. Inference power was augmented by the implemented of this function, and optimum for suboptimum solutions were obtained. Processing time with CBR is considerably shorter than other methods, and this feature is remarkable with complicated cases.
Economic evaluation of a photovoltaic power generation introduced into an electric power system with electricity storage
Authors: Nishikawa Yoshikazu , Tezuka Tetsuo , Kita Hajime , Kang Moon‐Sung 
Published: July 2007

AbstractRenewable energy utilization and electricity storage will soon be introduced into the conventional electric power system. This study assumes that a photovoltaic (PV) power generation system, a set of the PV units, is installed into the electric power system with electricity storage; moreover, the effects of uncertain variation characteristics of the PV system output on the operations of the conventional power generation system and the storage units are evaluated by simulations, with cost a major consideration. According to the simulation results, it is clearly demonstrated that the costs of the PV system are influence sharply by the prediction accuracy of their output.
A method of large‐scale control system design aided by system visualization technology
Authors: Myoi Takeshi , Amari Haruo , Hayashi Tatuo , Inamura Kouhei , Koike Hideki , Kuzuola Hideaki , Hirose Michitaka , Ishiii Takemochi 
Published: July 2007

AbstractProgress in computer and communication technology has made it possible to construct a large‐scale control sytem. However, expansion of such a control system will make it more difficult to design control software. In designing a large‐scale control system, it is hard to understand the data flow and synchronization of tasks and messages between computers. To solve this problem, we are developing a system to visualize control software for accessing information about the performance of the entire control system accurately and easily.This paper describes the characteristics of large‐scale control systems, the method of its visual representation and configuration, the role of the visualization tool, and the efficiency of the visual design method.
Electrical properties of TiO2 thin films prepared by the sol‐gel method
Authors: Yoshimura Noboru , Itoi Masashi , Sato Shigeki , Taguchi Haruo 
Published: July 2007

AbstractA TiO2 thin film was prepared by the sol‐gel method using a metal alkoxide [Ti(O‐i‐Pr)4 tetrasopropoxy titanium: TIPT]. The crystalline form of the film depends on the preparation conditions and the heat treatment temperature. When the ratio (γ) of H2O to TIPT is 7, the crystalline phase is formed at 400°C; when γ = 2 it is formed at 500°C. The anatase crystal structure was obtained for both γ = 2 and γ = 7. The electrical conductivity of the TiO2 film increased with the heat treatment temperature.
A voltage source PWM rectifier‐inverter with feedforward control of instantaneous power
Authors: Ogasawara Satoshi , Yamagishi Naoyuki , Totuka Hiroyuki , Akagi Hirofumi 
Published: July 2007

AbstractIn general, diode rectifiers with electrolytic capacitors on the dc side have been used as dc power supplies for voltage source inverters. This type of rectifiers, however, causes many problems such as poor power factor and harmonics. Recently, voltage source PWM rectifier‐inverters have been studied to provide the following advantages; (1) harmonic‐free on both ac sides; (2) unity power factor on the input ac side; (3) power flow of either direction or power regeneration; (4) reduction of the dc capacitor. It is, however, difficult for a conventional one to regulate the capacitor voltage on transient states because of having only a voltage feed‐back loop.This paper describes a voltage source PWM rectifier‐inverter with feed‐forward control of instantaneous power. Based on the pq theory, the instantaneous power which is calculated in the control circuit of the inverter is fed forward to the control circuit of the rectifier. The feed‐forward control of instantaneous power makes a great contribution to sufficiently suppress voltage fluctuation of the dc capacitor on transient states. Transient characteristics are discussed and some interesting experimental results of a laboratory model are shown.
High‐field dielectric properties of polyethylene in the high‐temperature region
Authors: Tokoro Tetsuroh , Tohyama Kazuyuki , Nagao Masayuki , Kosaki Masamitsu 
Published: July 2007

AbstractNonpolar polymers such as polyethylene or polypropylene are widely used as insulation materials, often under conditions involving strong electric fields and high temperatures. Under these conditions, the conduction loss due to DC‐like carrier transport may give rise to a high‐field AC dissipation factor (tan δ).This paper describes the high‐field dielectric properties of polyethylene films at frequencies from 50 to 400 Hz and temperatures from room temperature to 100°C, as measured with a new type electrode design developed by the authors. In the high‐temperature region, the AC dissipation current waveform at 50 Hz was also measured. At room temperature, the electric‐field dependence of tan δ is almost unaffected by the frequency of the applied field. But at high temperatures and strong electric fields, tan δ tends to have a large field dependence and to be almost inversely proportional to the frequency. Thus the AC conductivity becomes independent of the frequency of the applied field in the region of strong fields and high temperatures. A theoretical analysis shows that the high‐field dielectric loss is governed by two processes, namely, the dielectric relaxation loss inherent to the AC field and the DC‐like carrier transport loss that becomes prominent in the high‐temperature region, where AC dissipation current waveform becomes significantly nonsinusoidal.
Power system stability enhancement by static var system using self‐commutated inverters
Authors: Matsuno Katuhiko , Nagasawa Takashi , Ohtsuki Hiroshi , Ohnishi Shuichi , Ishiguro Fujio , Takeda Masatoshi 
Published: July 2007

AbstractThis paper deals with static var compensators using self‐commutated inverters (which is so‐called SVG) compared with conventional SVC and Rotary Condenser.Improvement of power system stability is explained by using simple system model and checked by dynamic digital simulation.In the latter part of this paper, system outline, basic specifications and control diagram of the SVG rated 154 kV, ±80 MVA, which has been installed at INUYAMA Switching Station, are briefly presented.Field tests at INUYAMA verify that power swing is effectively damped and transmission capacity is increased.
A combined engineering model for the analysis of switching surge flashover characteristics of long air gaps
Authors: Nishijima Kiyoto , Kanekiyo Tadamitsu , Asu Itaru Tsuney 
Published: July 2007

AbstractThe flashover characteristics of long air gaps submitted to switching surge voltages may be predetermined by use of a mathematical model of leader propagation.The present model is developed from each combination of previous engineering models, and is also applied to positive rod‐to‐plane geometries with gap lengths up to 20 m.However, four parameters to determine leader propagation with respect to our model are adjusted in the present calculation so as to fit experimental flashover voltages and calculated flashover voltages which depend on waveforms of the applied voltage and gap length. The calculations show that these parameters are only a function of gap length.Our combined engineering model using parameters that depend on gap length allows the flashover characteristics of long air gaps to be easily determined with a microcomputer.
A solution method using neural networks for the generator commitment problem
Authors: Sasaki Hiroshi , Fujii Yuuji , Watanabe Masahiro , Kubokawa Junji , Yorino Naoto 
Published: July 2007

AbstractThis paper studies the feasibility of applying the Hopfield‐type neural network to unit commitment problems in a large power system. The unit commitment problem is to determine an optimal schedule of what thermal generation units must be started or shut off to meet the anticipated demand; it can be formulated as a complicated mixed integer programming problem with a number of equality and inequality constraints. In our approach, the neural network gives the on/off states of thermal units at each period and then the output power of each unit is adjusted to meet the total demand. Another feature of our approach is that an ad hoc neural network is installed to satisfy inequality constraints which take into account standby reserve constraints and minimum up/down time constraints. The proposed neural network approach has been applied to solve a generator scheduling problem involving 30 units and 24 time periods; results obtained were close to those obtained using the Lagrange relaxation method.
The effect of space charge on the initial growth of electrical trees in polyethylene
Authors: Hozumi Naohiro , Okamoto Tatsuki , Imajo Takahisa 
Published: July 2007

AbstractThis paper describes the influence of space charge on the growth of an electrical tree which is an important factor of the dielectric breakdown in polyethylene‐insulated power cables. Polyethylene and ethylene vinyl‐acetate copolymer with a semi‐conducting needle were used as the treeing specimens. The statistical analysis showed that the growth rate and the unbalance of positive and negative partial discharges increased as the vinyl‐acetate content increased, and that the growth per cycle decreased with the increase in frequency. A model of the tree growth accompanied by the space charge behavior was proposed considering the above experimental results. The tree growth is considered to be caused by the dielectric breakdown due to the field enhancement at the tree tip during the positive half cycle of the applied voltage, the field enhancement being due to residual negative space charge injected during the previous negative half cycle. The negative space charge in polyethylene would be mainly supplied through the partial discharge inside the tree.
Evaluation of lightning fault rate of EHV transmission line based on lightning parameters derived from electromagnetic observation
Authors: Ishii Masaru , Hojo Jun‐Ichi 
Published: July 2007

AbstractCloud‐to‐ground lightning flashes in the Niigata area in Japan have been observed for a few years by a magnetic direction‐finder network. Data obtained so far are analyzed carefully taking into account the operating characteristics of the system. As a result, frequency distributions of return‐stroke current for each polarity are produced, and their seasonal variations and the occurrence probabilities of high current exceeding 200 kA are clarified.Based on the estimated current distributions, back‐flashover rates of 500‐kV 2 cct transmission lines are calculated. It is known that the back‐flashover caused by downward flashes can account for most of the line outages in the summer for both single‐ and multiple‐line faults. However, this mechanism cannot explain the high outage rate in the winter experienced in the winter thunderstorm area in the late 1970s. In spite of the low lightning flash density in the winter, the multiple‐line fault rate in the winter caused by back‐flashovers is predicted to be comparable to that in the summer, because of the seasonal variation of the frequency distributions of return‐stroke current.
An investigation of salt contamination on insulators and the effectiveness of pin‐type insulators with salt‐proof dishes
Authors: Higashimori Yoshio 
Published: July 2007

AbstractThis paper investigates the contamination of the surface of various insulators suspended in the air at a certain altitude and connected in series. It is shown that salt‐proof dishes attached to pin‐type insulators are effective against contamination.Exposure tests of insulators on Okinawa have been made since 1985 and the results are as follows:

The higher the placement of the insulator, the heavier the contamination.
The amount of contamination on the downward surface of the suspended insulators at the lowest position was considerably smaller than that of the insulators at the other positions.
The extent of contamination of the pin‐type insulators with the salt‐proof dishes was far less in comparison to that of pin‐type insulators without salt‐proof dishes.
The maximum equivalent salt‐deposit density was related closely to the small amount of precipitation during the observation period and the occurrence of high wind speed, which was higher than 10 m/s.
Low‐speed high‐torque drive system applying vernier motor torque
Authors: Ishizaki Akira , Shibata Yukiya , Watanabe Katsuyuki , Saitoh Kazuo 
Published: July 2007

AbstractThe application of the direct drive system is increasing in the field of robot and factory automation because of controllability with high accuracy. However, it requires the motor high torque at low speed.Although the vernier motor presented by Lee in 1963 could produce the reluctance torque in low speed, it involved many problems to be solved. This paper studies the reluctance torque of the vernier motor using the finite‐element field analysis. Since the increase of rotor slot number is effective in producing high torque, in the model here, there are not only winding slots but also small slots on the stator teeth surfaces. Also, the rotor slots are provided in the periphery of the core more than the total number of stator slots by the pole number. The calculated torques have agreed very well with the experimental results.A prominent feature of the control scheme is to control the armature current phase based on the detected rotor slot position. Thus there is no problem such as pull‐in or pull‐out in Lee's vernier motor. Then the instantaneous torque is controlled by the amplitude of armature current. The experimental results on both the speed control and the position control also are shown in this paper.
Sputter etching mechanism and changes of surface structure of PTFE
Authors: Yamamoto Suguru , Toyooka Masahide , Kubo Uichi 
Published: July 2007

AbstractGrowth of microscopic cones on PTFE surface by RF sputter etching process are studied. The surface texm changes from initial submicron hillocks to large cones during sputter etching. The height of these cones is 33 to 45 percent of the etching depth calculated from etching rate. The direction of these cones is nearly equal to the ion incident angle. Boundary energy of sputtering and growth of cones are 100 eV and 150 eV, respectively. It is obtained that the redeposition ratio by back diffusion to sputtered molecule is 11 percent from the experiment using collector. It is concluded that redeposition and repolymerization process of sputtered material occurs in parallel with the ion etching process, and cones continue to grow partly during etching.
Improvement of magnetic properties in Fe‐based nanocrystalline alloys by addition of Si, Ge, C, Ga, P, Al elements and their applications
Authors: Yoshizawa Yoshihito , Been Yoshio , Yamauchi Kiyotaka , Sugihara Hosaki 
Published: July 2007

AbstractMagnetic properties of Fe‐Cu‐Nb‐X‐B (X Si, Ge, C, Ga) and Fe‐Cu‐Nb‐Si‐B‐X (X: Ge, C, P, Ga, Al) nanocrystalline alloys were studied to improve soft magnetic properties and they were evaluated for some applications. Si was the best element for the Fe‐Cu‐Nb‐X‐B system. Substitution of P for B made the coercive force small in the Fe‐Cu‐Nb‐Si‐B‐X system having high saturation flux density. The cores using the Fe‐based nanocrystalline alloys showed low core loss, excellent dc superimposed characteristics and good noise attenuation characteristics. Hence, Fc‐based nanocrystalline alloys have high performance for such magnetic components as transformers and choke coils.