GB699791A - Improvements in electric circuit arrangements for operating high pressure metal vapour electric discharge lamps - Google Patents

Abstract

699,791. Automatic voltage control systems. GENERAL ELECTRIC CO., Ltd., and NELSON, E. H. April 13, 1950 [April 13, 1949], No. 10042/49. Class 38 (iv). [Also in Group XL (a)] An electric circuit arrangement including a high-pressure metal vapour electric discharge lamp in series with a stabilizing resistance for operation of the lamp from a D.C. supply if voltage V is such, the lamp containing a sufficiently large quantity of metal filling, that the voltage developed across the lamp when the lamp runs up after starting can, with suitably low or no cooling of the lamp envelope, attain a value V o considerably greater than V/2 without the metal being all evaporated, and such that the lamp is associated with cooling means adapted to cool the envelope or part thereof, and with control means responsive to the voltage developed across the lamp, said control means being arranged to render the cooling means operative or inoperative according as the lamp voltage increases or decreases from a value V 1 lying between V/2 and V 0 , whereby in operation the lamp voltage is maintained substantially constant at the said value V 1 . In the arrangement shown in Fig. 1 the control means comprises an electro-magnetically operated switch 9, the operating coil 8 of which is connected, in series with a rectifier 10, on one side to a point between the lamp 1 and a stabilizing resistance 4 in series with the lamp, and on the other side to a variable tapping 11 at voltage V 1 on a potentiometer resistance 7 connected across the lamp and the stabilizing resistance, so that, in operation, an increase in the lamp voltage from at least one value V 1 , lying between V/2 and V 0 , causes the switch 9 to be operated to cause the cooling means, which may comprise a fan arranged to blow air on to the lamp envelope, to cool the lamp. In the arrangement shown in Fig. 2 the cooling means comprise a cold spot provided on the lamp envelope, e.g. the side stem 14, and means for heating said cold spot, e.g. a resistance heating element 16 in the circuit of the switch 9, the rectifier being oppositely directed to the arrangement of Fig. 1. Specifications 266,489, 288,007, (both in Class 81 (ii)], and 344,072 [Group XL], are referred to.