Article

How to Keep the Temperature of a Hot Wire Constant

Review of Scientific Instruments

March 1972
43(3)

DOI:10.1063/1.1685659

Authors:

A method is described of stabilizing the temperature of a heated wire under changing conditions of cooling and evaporation. It depends on controlling the resistance of the wire by the use of a power supply having a special current-voltage characteristic. The characteristic has been obtained by a slight change in a normal commercial apparatus. The great advantage of the control is its simplicity. Application of a thermocouple or optical measurement of the temperature of the heated wire is not necessary. Measurements on a tungsten wire at 1100°C showed the temperature to change less than 10°C in spite of a 800&percnt; variation in the energy input. Working at constant voltage causes the temperature to change more than 200°C by this input variation. The method can be applied to electrical furnaces, degassing of metals, electromotors, hot filament ionization of gases, etc. Variations in cooling rate require a different voltage-current characteristic of the power source than does evaporation or aging of the wire.

Heat transfer—A review of 1972 literature

Article

Nov 1973
INT J HEAT MASS TRAN

ResearchGate has not been able to resolve any references for this publication.

Article

Kilohertz range pulsed x-ray generator having a hot cathode triode

April 1991 · Proceedings of SPIE - The International Society for Optical Engineering

The fundamental studies for the repetitive pulsed x-ray generator utilizing a hot cathode triode operated at high repetitive rates in the kllz-range are described. This generator consisted of the followingessential components: a constant high- voltage power supply, an energy storage condenser, a grid pulser, a DC-DC converter for supplying grid bias voltages, and an x-ray tube. The x-ray tube ... [Show full abstract] was of an enclosed-triode type and consisted of the following devices: an anode rod made of copper, a plane anode tip (target) made of tungsten, a grid made from tungsten wire, a focusing electrode made of iron, a hot-cathode (filament) made of tungsten, and a glass body. The condenser which was attached to the anode electrode was charged from 50 to 70kV, and the electric charges in the condenser were discharged repetitively by the grid electrode operated by the grid pulser. The pulse width was primarily determined by the pulse width from the grid pulser, the grid bias voltage, and the cut-off voltage for thermoelectrons, and could be controlled to about ips. The x-ray pulse height primarily increased according to increases in the charged voltage at a constant grid bias voltage. The x-ray intensity was 1. 35nC/kg at 0. 5m per pulse with a condenser charged voltage of 70kV, a grid bias voltage of -1. 0kV, and the charged voltage of the grid pulser of 400V.

Article

Short Sample Test of Superconducting Wire

July 1975 · IEEE Transactions on Nuclear Science

Two different techniques were used for short sample tests of superconducting wires. One method was done with a DC transformer and the other with a high current DC power supply. Three different types of sample holders were used for the latter. Their relative merits and demerits are compared. Many wire designs representing half a dozen companies have been tested, and their results are presented. ... [Show full abstract] For the short sample test, quench current and current at various resistivities was determined. Resistivity ratios of Â¿300/Â¿12 were found for copper, and the effect of cola work on these ratios was investigated.

Article

Full-text available

Comparação do desempenho operacional e das características do cordão na soldagem com diferentes aram...

March 2009 · Soldagem & Inspeção

This paper compares the bead characteristics of welds deposited of carbon steel tubular wires. Three tubular wires of 1.2 mm produced in Brazil were used: rutilic (ASME SFA-5.20: E71T-1/E71T-9/E71T-9M), basic (ASME SFA-5.20: E71T-5/E71T-5M) and metal cored (ASME SFA-5.18: E70C-3M). Welding trials were performed in downhand position on thick (12 mm) low-carbon steel plates using a constant voltage ... [Show full abstract] power supply. Welding current and voltage, and wire feed rate were monitored in all trials. For each tubular wire type, the shielding gas composition (75%Ar-25%CO2 and 100%CO2) and wire feed rate (7 and 9 m/min) were changed, and other process variables, including electrode polarity (CC+), electrode and arc lengths (16 mm and 3.5 mm, respectively) were kept constant throughout the experimental program. Weld bead geometry parameters (penetration depth, reinforcement, width, fused and deposited areas, and weld dilution), presence of weld discontinuities, fusion zone microstructure and hardness were measured and compared for the different tubular wires. Operational conditions that yielded weld bead characteristics favored for the welding of thick plates of structural steels were determined.

Conference Paper

Application of a SMES to protect a sensitive load in distribution networks from two consecutive volt...

April 2010

Nowadays, many electrical systems are practically sensitive to short power disturbances and voltage sags. Since three decades ago, many research of superconducting magnetic energy storage (SMES) system have been doing to improve power quality of sensitive electric systems. The objective of this paper is to present the modeling and analysis of a SMES to protect a sensitive load in Azarbayjan ... [Show full abstract] distribution network from consecutive voltage sags. The topology of the SMES system and its response to two consecutive voltage sags are described. Simulation results reveal the effectiveness of the proposed controller.

Article

Fast, Nonspattering Inert-Gas Welding

March 1991

Jeffrey L. Gilbert

Proposed welding technique combines best features of metal (other than tungsten)/inert-gas welding, plasma arc welding, and tungsten/inert-gas welding. Advantages include: wire fed to weld joint preheated, therefore fed at high speed without spattering; high-frequency energy does not have to be supplied to workpiece to initiate welding; size of arc gap not critical, power-supply control circuit ... [Show full abstract] adjusts voltage across gap to compensate for changes; only low gas-flow rate needed; welding electrode replaced easily as prefabricated assembly; external wire-feeding manipulator not needed; and welding process relatively forgiving of operator error.

Article

Fabrication of a Rotor for a Field Based, Self-Excited Compulsator Power Supply for a 9 MJ Railgun D...

February 1993 · IEEE Transactions on Magnetics

Fabrication of a high-speed, self-excited air-core rotor for a field based compulsator is well under way. The compulsator is to be used as a power supply for firing 9 MJ projectiles from a skid mounted electromagnetic launcher (railgun). The rotor flywheel is made of fiber reinforced epoxy composite and is supported with high-strength metal stub shafts which are shielded from the excitation field ... [Show full abstract] by water-cooled copper sleeves. The rotor features separate windings for self-excitation and railgun firing, and a two-pole configuration for pulse length considerations. The rotor is designed to store 210 MJ at 8600 r/min, with a rating of 3.2 MA peak current and 20 GW peak power into a 9 MJ railgun load. The concentric fiber-reinforced epoxy composite rings that make up the rotor flywheel are filament wound on steel mandrels, cured, and interference fit together. The main and excitation armatures and output conductors leading from the armatures to the shaft conductors are constructed of epoxy-impregnated aluminum and copper Litz wire

Article

Full-text available

Experimental Research of Micro-Arc Discharge Phenomena.

November 2000 · QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY

Features of microseconds arc discharge with gap spacing of micrometers, between a cathode of thin tungsten wire with sharpened tip and an anode of stainless steel plate, have been experimentally investigated. The experimental setup, which consists of a micro-arc torch, precise positioning mechanisms actuated by piezoelectric devices and pulse motors, and a power supply for discharge, was ... [Show full abstract] constructed. Time-resolution of micro-discharge appearance was observed through microscope with high-speed shutter CCD camera. It is shown that gap length is dominant factor of not only electrical breakdown voltage but also size and/or form of melting spot at anode surface by micro-arc.

Article

Some characteristics of tungsten filaments operated as cathodes in a gas discharge

April 1979 · Review of Scientific Instruments

Some physical properties of tungsten filaments, when operated as cathodes in a gas discharge, are presented. For a 0.1524-cm-diam tungsten wire, the initiation of a discharge is found to be dependent on the filament geometry. The effect of connecting the discharge power supply to either the positive or negative leg of the filament is examined. When the emission current becomes a sizable fraction ... [Show full abstract] of the filament heater current, the filament does not emit uniformly. The temperature distribution indicates that the majority of the electrons are emitted from the negative leg of the filament.

Article

Arc Behavior and Droplet Transfer Process of VP CMT

December 2013 · Applied Mechanics and Materials

Cold metal transfer (CMT) is widely used in thin sheets welding, owing to its low heat input and freedom of spatter. An evolutionary technology, called CMT Adv, combines CMT and variable polarity (VP) process. Arc behavior analysis and droplet transfer analysis were performed by image capture system synchronized with current and voltage sensor. Checker calibration method was used to get ... [Show full abstract] dimensions of droplets. The results show that motion of filler wire, current and voltage waveform and droplet transfer of VP CMT (CMT Adv) are coordinated to maintain welding stability. And through precise energy control, droplets of same dimensions can be got in EP and EN period, which are similar to diameter of filler wire. To from droplets with same dimensions, lower power was supplied and melt efficiency is higher in EN period.

Article

Full-text available

Comparação do desempenho operacional e das caracter��sticas do cordão na soldagem com diferentes ara...

December 2011 · Soldagem & Inspeção

This paper compares the bead characteristics of welds deposited of carbon steel tubular wires. Three tubular wires of 1.2mm produced in Brazil were used: rutilic (ASME SFA-5.20: E71T-1/E71T-9/E71T-9M), basic (ASME SFA-5.20: E71T-5/E71T-5M) and metal cored (ASME SFA-5.18: E70C-3M). Welding trials were performed in downhand position on thick (12 mm) low-carbon steel plates using a constant voltage ... [Show full abstract] power supply in negative wire polarity (CC-). Welding current and voltage, and wire feed rate were monitored in all trials. For each tubular wire type, the shielding gas composition (75%Ar-25%CO2 and 100%CO2) and wire feed rate (7 and 9 m/min) were changed, and other process variables, including electrode and arc lengths (16 mm and 3.5 mm, respectively) were kept constant throughout the experimental program. Weld bead geometry parameters (penetration depth, reinforcement, width, fused and deposited areas, and weld dilution), presence of weld discontinuities, fusion zone microstructure and hardness were measured and compared for the different tubular wires. Operational conditions that yielded weld bead characteristics favored for the welding of thick plates of structural steels on negative wire polarity were determined.

Conference Paper

Instrumentation and methodology for revision of European flicker threshold

November 2002

The European standard CENELEC EN 50160 establishes that the severity of flicker caused by voltage fluctuations, under normal operating conditions, will not exceed the long term severity Plt=1 during 95% of the time in one week. This threshold was originally established considering that a lamp with tungsten filament of 60 W and 240 V, produces a flicker perceivable by 50% of the population when it ... [Show full abstract] is supplied with a voltage that verifies Plt=1. This work makes an analysis of this threshold, establishing as hypothesis the fact that incandescent lamps have little use nowadays, specially in industrial and commercial environments. In order to make a revision of the current thresholds, we have proposed an electro-optical equipment and the associated methodology. The device simulates the behavior of the eye plus human brain set, avoiding large clinical experiments. A methodology is also proposed in order to characterize the perceptibility threshold of a generic lamp. Finally, the proposed instrumentation and methodology is applied to two types of lamps: incandescent and fluorescent.

Article

Full-text available

Design and construction of a bipolar pulsed-dc power supply for magnetron sputtering systems

January 1970

A bipolar pulsed-dc power supply has been designed and constructed for use in a magnetron sputtering system and for thin film synthesis. The power supply consists of three major parts: (1) two high voltage direct current power supplies utilizing a phase control circuit for power delivery, (2) a pulse generator and two power switching circuits, and (3) feedback circuits for current and voltage ... [Show full abstract] controls, displays, and safety measures. For a high level of safety operation, optical connections were employed in the circuit design for complete isolation between low and high voltage sections. The constructed power supply was tested using a test load consisting of ten 100 W 250 V light bulbs with tungsten filaments connected in series. It was found that the power supply was capable of supplying either symmetric or asymmetric pulsed-dc power of maximum peak-to-peak voltage of 1250 V. The negative and positive pulse widths were selectable between 10-100 μs, with a maximum pulse frequency of 30 kHz. This frequency limit is due to the limited speed of the power transistors used in the power switching circuit operating at high voltage. It is anticipated that the constructed power supply can be used as a plasma generator in a magnetron sputtering system for the deposition of oxide thin films such as Al 2 O 3 , Na x Co 2 O 4 , ITO and ZnO.

Last Updated: 22 Oct 2024