Simulation Analysis of Critical Parameters for Thermal Stability of Surge Arresters

Metal oxide varistors are applied today inside modern surge arresters for overvoltage protection for all voltage levels. Their main issue is the thermal activation of their crossing current, which could lead to complete destruction by thermal runaway. This article presents a new technological solution developed in order to increase the thermal stability of metal oxide varistors. It consists in connecting in parallel two or more similar varistors (for dividing their current), having a thermal coupling between them (for equalizing their temperatures and forcing them to act together and simultaneously as much as possible). Starting from a finite element computer model performed for each situation (varistor standalone or parallel), up to real measurements, the thermal stability of the equipment was analyzed in permanent and impulse regime. Experiments were carried out in the same conditions. Experimental data obtain from two disk varistors corresponds very well to simulations, proving that parallel connection of varistors, combined with a thermal exchange between them is an efficient technical solution for thermal stability improvement, even if not apparently economically justified.

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A Simulation Analysis Research on the Material Performance of Resin Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.721.135 ◽

2013 ◽

Vol 721 ◽

pp. 135-138

Author(s):

Bo Wang ◽

Bin Lin ◽

Kun Zhao

Keyword(s):

Thermal Stability ◽

Thermal Expansion ◽

Numerical Analysis ◽

Thermal Expansion Coefficient ◽

Cross Section ◽

Expansion Coefficient ◽

Simulation Analysis ◽

Analysis Method ◽

Accumulation Model ◽

Thermal Stability Of

A numerical analysis method of the thermal stability of the resin concrete is proposed in this paper. A 3D aggregate accumulation model based on the predecessors theory is established and a 2D cross section is directly captured from it. In order to simplify the analysis, a kind of conversion program is developed. The thermal expansion coefficient of established model is close to previous research results. It confirms the analysis method is correct. By the results, a reliable formula is found to calculate the thermal expansion coefficient and a method to reduce the thermal expansion coefficient of resin concrete is proposed.

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Thermal Stability of a Vertical Fluid Layer With Volumetric Energy Source

Journal of Heat Transfer ◽

10.1115/1.3247465 ◽

1985 ◽

Vol 107 (3) ◽

pp. 589-595 ◽

Cited By ~ 2

Author(s):

A. H. Shaaban ◽

M. M. O¨zis¸ik

Keyword(s):

Energy Source ◽

Thermal Stability ◽

Prandtl Number ◽

Traveling Waves ◽

Fluid Layer ◽

Critical Parameters ◽

Energy Sources ◽

Critical Curves ◽

Prandtl Numbers ◽

Thermal Stability Of

The effects of nonuniform volumetric energy sources on the thermal stability of natural convection in a vertical fluid layer are investigated using the linear theory of stability. The neutral states of stability are obtained for four values of Prandtl number, ranging from 0.71 to 100, and for different values of β in the range 0.1 ≤ β ≤ 10. The critical parameters and the energetics of the critical disturbances are determined for each case. For all values of Prandtl number and β studied here, the critical instabilities set in as traveling waves, moving in the direction of gravity. In the low range of Prandtl number, 0.71 to 5, the critical curves approach the same asymptotic value for β ≥ 10. The critical disturbances are found to be buoyancy driven for all Prandtl numbers and β considered here, except for the low range of Prandtl number, for which they become shear driven disturbances as β increases.

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The Ordered Phase Formation in Ti-Al-Ga Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069193 ◽

1970 ◽

Vol 28 ◽

pp. 440-441

Author(s):

Shiro Fujishiro ◽

Harold L. Gegel

Keyword(s):

Thermal Stability ◽

High Temperature ◽

Titanium Alloys ◽

Growth Kinetics ◽

Stoichiometric Composition ◽

Good Potential ◽

Alpha Titanium ◽

Cold Rolled ◽

Kinetics Of ◽

Thermal Stability Of

Ordered-alpha titanium alloys having a DO19 type structure have good potential for high temperature (600°C) applications, due to the thermal stability of the ordered phase and the inherent resistance to recrystallization of these alloys. Five different Ti-Al-Ga alloys consisting of equal atomic percents of aluminum and gallium solute additions up to the stoichiometric composition, Ti3(Al, Ga), were used to study the growth kinetics of the ordered phase and the nature of its interface.The alloys were homogenized in the beta region in a vacuum of about 5×10-7 torr, furnace cooled; reheated in air to 50°C below the alpha transus for hot working. The alloys were subsequently acid cleaned, annealed in vacuo, and cold rolled to about. 050 inch prior to additional homogenization

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Microstructure studies of tungsten silicide schottky contacts on Gaas

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126445 ◽

1987 ◽

Vol 45 ◽

pp. 328-329

Author(s):

Yih-Cheng Shih ◽

E. L. Wilkie

Keyword(s):

Thermal Stability ◽

Field Effect Transistors ◽

Schottky Contact ◽

Schottky Contacts ◽

Excellent Thermal Stability ◽

Barrier Heights ◽

Gaas Substrates ◽

Film Adhesion ◽

Threshold Voltages ◽

Thermal Stability Of

Tungsten silicides (WSix) have been successfully used as the gate materials in self-aligned GaAs metal-semiconductor-field- effect transistors (MESFET). Thermal stability of the WSix/GaAs Schottky contact is of major concern since the n+ implanted source/drain regions must be annealed at high temperatures (∼ 800°C). WSi0.6 was considered the best composition to achieve good device performance due to its low stress and excellent thermal stability of the WSix/GaAs interface. The film adhesion and the uniformity in barrier heights and ideality factors of the WSi0.6 films have been improved by depositing a thin layer of pure W as the first layer on GaAs prior to WSi0.6 deposition. Recently WSi0.1 has been used successfully as the gate material in 1x10 μm GaAs FET's on the GaAs substrates which were sputter-cleaned prior to deposition. These GaAs FET's exhibited uniform threshold voltages across a 51 mm wafer with good film adhesion after annealing at 800°C for 10 min.

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