Showing papers by "Mitsubishi Electric published in 1974"

Area Effect of Electrical Breakdown in Compressed SF6

Abstract: This paper presents experimental results on the statistical properties of ac and dc breakdown field strength of compressed SF6. The experiment is performed on four gaps of different electrode area, ranging from 0.2 cm2 to 3000 cm2. Patterns of breakdown characteristics are classified into four categories depending on the type of distribution and the characteristics of conditioning effect. The criterion of the transition of these categories are discussed quantitatively.

Effect of Solid Impurities on Breakdown in Compressed SF6 Gas

Abstract: In compressed gas insulated systems, the problems of the conducting particles, which are suspected to cause the irregular breakdown in SF6 gas, are serious matter for design engineers. In this paper the effects of conducting particles and insulating fibers are described under alternating, impulse and alternating-impulse superposed voltage conditions. Those investigated results had been applied for 500kV gas insulated substation already put into service in Japan.

Study of Tin Diffusion into Silicon by Backscattering Analysis

Abstract: Diffusion of tin into Si from tin-doped oxide is studied by the backscattering and channeling analyses. The depth distribution of tin in Si can be fitted to complementary error functions. The diffusion coefficient can be expressed as D=0.054exp (-3.5eV/kT). The solubility limit in Si and the segregation constant between Si and SiO2 are estimated to be 6~8×1019/cm3 and 0.066 at 1100°C~1200°C, respectively. The lattice location of tin in Si is also determined by angular scan, and it is found that more than 90% of tin atoms occupy substitutional sites. Uniformity of the concentration over a silicon wafer is also checked with the microanalysis system by using backscattering and is found to be good. Effect of post-diffusion of phosphorous or boron on the depth profile of tin is also studied.

Protection of Motor from Switching Surge by Vacuum Switch

Abstract: A way of surge suppression by a reactor is presented for the protection of turn-to-turn insulation of motors from steep front surges produced by vacuum switch. In the first part of this paper, the construction and the functions of the reactor are explained. Discussions are given on the possibilities of turn-to-turn faults by the switching surges under the effect of the reactor, taking voltage distribution in motor winding into account. The result is expressed as the probability of turn-to-turn fault per switching operation for a given circuit condition. Examples of numerical evaluation of probability are obtained for a circuit breaker with average chopping current of 4A and for a contactor with average chopping current of 1 A.

Frequency response of Ga 1-x Al x As light-emitting diodes

Abstract: Frequency responses of Ga 1-x Al x As light-emitting diodes with various Al composition are measured. When the emission peaks become shorter than 7000 A, the cutoff frequencies decrease abruptly from 15 MHz to 5 MHz. A conclusion is that the frequency response is determined mainly by the lifetime of injected electrons which changes along with the Al composition because of the distribution of electrons between the Γ and X valleys.

Estimation of the Size of Voids in Coil Insulation of Rotating Machine

Abstract: Voids produced in the impregnation process exist in mica insulation system of rotating machine coil. Distribution of those voids' size, gap spacing, and discharge area is estimated based on the experimental data on the repetition rate and the apparent charge of partial discharges of sample coils. The method is grounded on several assumptions such as Paschen's law for discharge inception voltage of the voids, zero residual voltage after the discharge. These assumptions are verified for model voids. A computer program was developed to obtain the void size distribution rapidly and accurately. The size of voids detected in-practical model coils are in the range of gap spacing and discharge area of 0.01 mm~0.2 mm and 5 mm2~300 mm2, respectively. The results are in conjunction with the tip-ups of tangent delta and also compared with the results of a method developed by Terase [1].

Characteristics of the Junction-Stripe-Geometry GaAs-GaAlAs Double-Heterostructure Lasers

Abstract: A new junction-stripe-geometry DH laser has been examined, in which the current is confined into a narrow stripe by p-n junctions. Because of the difference in the diffusion potentials between two kinds of p-n junctions, a large portion of the current flows across the junction of the lower diffusion potential. It is shown that to obtain sufficient confinement of the current for lasing, the difference of diffusion potentials should be larger than 0.35eV, and the series resistance at the stripe region less than 1×10-4Ωcm2. The minimum threshold currents are 160mA and 270mA in pulse and cw operations, respectively. The effect of the stripe width has been examined, and the optimum value of about 6 µm is found, in which case relatively homogeneous lasing occurs, and the lateral spreading of carriers has little influence on the threshold current.

A modification of the constructive asymptotically good codes of Justesen for low rates

Abstract: Modifying the block codes proposed by J. Justesen, we propose another class of constructive asymptotically good block codes. The codes are constructed by the second-order concatenation, where the ensemble of the first-stage codes is Wozencraft's ensemble of randomly shifted codes, the second-stage codes are Reed-Solomon codes and the third-stage code is a Reed-Solomon code. The asymptotic lower bound of the ratio d/n of the minimum distance d to the code length n of the block codes is larger than that of Justesen's block codes for rates lower than 0.035, and is larger than that of the low rate Justesen codes discussed by E. J. Weldon, Jr. for rates lower than 0.015. Furthermore, as the rate approaches 0, it approaches 0.5 of the Varsharmov—Gilbert bound faster than that of the Weldon codes. Applying the same method to Justesen's convolutional codes, we construct another class of constructive asymptotically good convolutional codes. The asymptotic lower bound of the ratio dfree/nA of the free distance dfree to the constraint length nA of the convolutional codes is larger than that of Justesen's convolutional codes for rates lower than 0.23.

Dynamics of a Spin-Stabilized Satellite Having Flexible Appendages

Abstract: This paper deals with the dynamic features of a spin stabilized satellite having flexible appendages. The satellite is assumed to be constituted as a central rigid body and flexible appendages attached in the spin plane. The analysis is based on the method of averaging. The decay time constant for nutational body motion derived as the first-order solution of this method is the same as the result obtained by the energy sink method. The second-order decay time constants obtained by this method are in good agreement with numerically computed solutions over a range of parameter values for which corresponding results obtained by the energy sink method are not accurate. Analytical stability criteria are also obtained. Furthermore, the heavy damping characteristics of nutational body motion due to nonlinear internal resonance are investigated analytically by this method, and a closed form solution is obtained.

Effects of the element pattern on the directive properties of a scanning planar array

Abstract: An approximate expression is derived for a shift of a main-beam direction due to its element pattern in a uniformly illuminated, scanning planar array for a sin^{p} \theta \cdotp sin^{q} \phi element pattern. Furthermore, the integral of the radiation power pattern of the array is approximately evaluated, and discussions are given about the effect of the element pattern on the scanned directivity of the array. Numerical results are presented for several cases.

Behavior of ionic conduction in poly(methyl methacrylate under a high electric field.

Abstract: Electrical conduction of poly (methyl methacrylate) (PMMA) is considered to be ionic from low to very high fields near breakdown. Support for the ionic mechanism can be supplied from the compensation law, and from the temperature dependence of the electrical conductivity and the breakdown field. In high electric fields above the ohmic region, it was observed that the apparent activation energy decreased with increasing electric field. A simplified equation for the activation energy was derived in which the dependence of the electric field on ionic jump energy and ionic dissociation energy was taken into consideration. The ionic jump distance between equilibrium positions computed from the equation was 10 to 20 A and was in good agreement with periodic structure of PMMA.

Study of Solid Surfaces by Electron Impact Desorption Technique

Abstract: 電子衝撃脱離 の実験方法 は電 子衝撃 によって生 ずる表 面の物理 的または化学的 な変化 を直接検出す る方法 とそ れに伴 って脱離す る粒子(イ オ ン,中 性粒子,準 安定粒 子)を 検 出す る方法 との二つ に区分で きる.以 下に これ らの方 法及び特長 について述べ る.入 射電子には試料 の 状態 が影響 を受 けない よ うな 微 少 電 流(10-6~10-4A /cm2)を 用い るが,特 に電子衝 撃効果 を調 べ る 際 に は 10-4A/cm2以 上 の電 流 を用い ることがある.測 定 は全 て 到達圧力が1×10-9 Torr以 下の 超高真空装置 を 用 いて 行 な う2). 2.1 表面状態の変化 を直接検 出する方法 これは電子衝 撃 とフラッシ ュ脱離法,仕 事関数測定, 電界 電子放射 法,低 速 電子線 回折法,オ ージ ェ電 子分光 法等 とを組 合せた方法 である.こ れ らの方法で測定 した 物理 的 または化学的変化量 の定量的解釈 を行 な う場合 に は変 化量 が 影響 を受 けた 表面被 覆度(surface coverage) に比 例す ると仮定す る. ある吸着状態 にN個/cm2の 吸着粒子があ る場 合, n 個/cm2secの フラ ックスの電子線 による表面被覆 度の時 間変化 の割合 は再吸着 を無視す ると, ( 1 ) で与 え られ る.こ こでQは 電子衝 撃過程の 全 断 面 積 (cm2)と 呼ぶ. (1)式を積分す る と, ( 2 ) となる.こ こでJは 電子電流密度(A/cm2),eは 電子 の電荷(C),N(t)は 電子衝撃 開始後時 間'(sec)に おける

Apparatus for electrolytically etching a workpiece

Abstract: A method and apparatus for electrolytically etching a workpiece by controlling the working voltage by means of a factor proportional to the ratio of the amount of electrolyte to that of gas within the working gap. The working voltage is so controlled to properly change the specific resistance of the electrolyte and thereby accurately maintain the distance of the working gap at a constant and predetermined value.

Temperature Raise Control of Super Critical Boiler Using Derivative Digital Filter

Abstract: A DDC algorithm for raising the temperature of water wall outlet fluid of super critical boilers at the start up is proposed and some results of its implementation to a super critical boiler for the test purpose are presented.

MDSS, A Real-Time Problem-Oriented Programming System with Conversational Tuning Facilities

Abstract: MDSS, MELCOM DDC & SUPERVISORY-CONTROL SYSTEM, is a comprehensive operating system with a problem-oriented language, developed for improving conventional procedural programming languages like FORTRAN in the aspects of compact description of process data monitoring and execution control of program tasks, and program documentation.

Deformation of a Laminated Cylindrical Rotor

Abstract: This paper describes the behavior of slip, force transmission mechanism and deformation of a laminated cylindrical rotor composed of segmental sheets under circumferential tensile force caused by centrifugal force. Experimental and theoretical investigations have been made and the results of experiments on slip between the sheets and deformation of cylinder have been consistent with the theory. Dimensions and arrangement of the segmental sheets, tightening pressure of the laminated cylinder and tightening-bolt holes in the sheets have effects on the behavior of slip and deformation of the laminated cylinder, and these effects are herein discussed.

Dynamic mechanical properties of cured epoxy resin filled with mica flake

Abstract: Dynamic mechanical properties of cured epoxy resins filled with small mica flake were investigated.