GB762489A - Improvements in or relating to electric circuit arrangements for starting and operating at least one low pressure electric discharge lamp - Google Patents

Abstract

762,489. Supply systems for space discharge lamps. GENERAL ELECTRIC CO., Ltd., and CATES, J. Jan. 5, 1955 [Oct. 7, 1953], No. 27556/53. Class 38 (4). At least one L.P. electric discharge lamp 9 having two heatable electrodes 7, 8 is started and operated from an A.C. supply by a circuit comprising an electrode heating transformer 22 having its primary winding 23 connected directly between the circuit input terminals 1, 2 and at least one secondary winding 25, 26. connected to respective lamp electrodes 8, 7 to supply heating current thereto, and connections between the lamp electrodes and the input terminals, or, as shown, wherein the transformer has an autoconnected main secondary winding 23, 24, between the latter winding and the electrodes, for supplying the lamp discharge current; these connections include an inductor 10 which forms part or the whole of the lamp's ballast impedance, is magnetically separate from the transformer, and is connected so as to be between one 7 of the lamp electrodes and one input terminal or as shown the free end of the main secondary winding, and a capacitor 12 is connected so as to be between a tapping 11 on the inductor 10 and the other input terminal 2; the capacitor 12 and tapped off part 11<SP>1</SP> of the inductor 10 in series therewith between the input terminals form a non-resonant starting circuit for applying between the lamp electrodes a voltage pulse generated by the charge current of the capacitor 12 and stepped up by the autotransformer action of the tapped inductor 10. The capacitor 12 also serves to correct the power factor, the overall ballast impedance may be capacitive, and an earthed starting strip 13 may be provided. Instead of both electrodes being heated by secondary windings one may be serially connected between the capacitor 12 and the input terminal 2. Embodiments are disclosed wherein a pair of lamps are connected in parallel, and in which each lamp is replaced by a chain of lamps in series. The switch, not shown, by which the circuit is connected to the supply is preferably of such type which makes and breaks a number of times in one operation, to ensure lamp starting should the instantaneous value of the supply voltage be low when the switch contacts first make. The construction and values of circuit components are described.