GB726891A - Improvement in electrical discharge lamp - Google Patents

Abstract

726,891. Supply systems for space discharge devices. KREFFT, H. E. June 26, 1950 [July 19, 1949], No. 16906/50. Class 38 (4). [Also in Group XL (a)] A super-high pressure discharge lamp having one to four necks contains a rare gas such as krypton or xenon with or without mercury and with or without other metals such as cadmium, zinc or thallium, at an operating pressure of about 10-30 atmospheres, at least one pair of main electrodes, at least one pair of pilot electrodes, and preferably a starting electrode. A circuit for the lamp is shown in Fig. 5, the main electrodes 8 and the pilot electrodes 14, 14<SP>1</SP> being connected through ballasts or resistances 22, 23 and switches 24, 25 in parallel to a voltage source 26 supplying single-phase alternating or direct current. The starting electrode 13 is connected to the secondary coil of a transformer 27. The lamp may contain four or any number of pairs of solid incandescent main electrodes arranged in two sets and in one plane or each set of electrodes arranged to form two rows, a triangle or a square, and a pair of solid incandescent actuated pilot electrodes. The lamp may have two sets of three main electrodes, each set being arranged in a triangle, the pilot electrodes being arranged along the lamp axis and closer to the necks of the lamps than the main electrodes. The circuit shown in Fig. 5 can be used or a three-phase four-wire system when the neutral conductor is connected to the pilot electrodes while the phases are connected through ballasts to the main electrodes. Two separate three-phase systems which are electrically independent can be used. In a modification, the lamp is provided with two pairs of main electrodes and one pair of pilot electrodes of the pre-heated type. Specification 687,297, [Group XL (a)], is referred to.