GB1347091A - Electric arc starter - Google Patents

Abstract

1347091 Arc heating UNION CARBIDE CORP 3 May 1971 [4 May 1970] 12666/71 Heading H5H [Also in Divisions F1 and H1] An electric arc device, e.g. a heat source which includes electrodes 20, 22 within a cylindrical chamber 18 which are provided with coaxial bores 60 and 62 respectively comprises a starter rod 38 located such that it can be extended through the bore in electrode 20 to enter the opposed electrode bore 62 and retracted to start the arc discharge. The starter rod is moved by means of gas from a supply which is introduced through conduit 52 and gas openings 42 into piston chamber 35 where it acts upon piston 36 attached to the starter. The piston comprises a non-conducting member 50 which acts as a fluid seal. When the starter rod is extended between the electrodes an inert gas, e.g. A, Kr, Xe is introduced into the quartz envelope 16 of the arc device through openings around the circumference of electrode 20 causing the gas to swirl inwardly from the electrode. The gas vortex causes the starter rod to rotate within the electrode bores after which a relatively low voltage is applied between the electrodes, connecting electrode 20 to the negative terminal. The pressure behind piston 36 is then released to retract the starter rod, thereby extending the arc between the electrodes. The gas vortex serves to constrict the arc and cools the quartz envelope. A control system is provided (Figs. 2, 3, not shown) in which a common recirculating gas supply is used to fill the discharge envelope and to move the starter rod and in which the stages of starting the arc discharge are sequentially controlled. Operating sequences are discussed in detail in respect of Fig. 2, providing for example a slow build up of swirl flow. Bleed through valve (98) regulates delivery pressure, a reduced pressure minimizing the starting voltage. The starter rod may be made of tungsten or 2% thoriated tungsten, the anode 22 of copper, and the cathode 20 of an outer body of copper with a tungsten or thoriated tungsten inner layer adjacent the arc chamber. Cooling fluid such as water is passed through passages in the manifold assemblies 12, 14 at each end of the arc chamber. The gas pressure need not be regulated during the starting interval, the exhaust gas may be vented into the atmosphere rather than recirculated and a separate supply may be used for the starter assembly.