GB1500569A - Low pressure sodium discharge lamp starting and operating circuit - Google Patents

Abstract

1500569 Starting circuits for gas discharge lamps J CATES 13 Aug 1975 33688/75 Heading H2H A circuit arrangement for starting and operating a gas discharge lamp such as a low pressure sodium vapour lamp 1 comprises input terminals 3, 4 connected to an A.C. source, a power factor correction capacitor 9 connected across the imput terminals, a further capacitor 13 connected across a pair of output terminals which are connected to the lamp 1, an inductive ballast connected, in series with the heating coil 12 of a thermally operable switch 11, between the input terminal 3 and an output terminal, the normally closed terminals of the switch 11 being connected in series with a capacitor 6 and a resistor 7, which series circuit is connected in parallel with the capacitor 13 and a device 14 connected in parallel with the heating coil 12 to limit the current flowing in the coil 12 to a predetermined value. The device 14 may be a thermistor, with a negative temperature coefficient, or a saturable reactor and a capacitor 8 is connected across the contacts of the switch 11. In other embodiments, the inductive ballast may be divided into two serially connected parts and the A.C. supply may be connected to an autotransformer which supplies the circuit arrangement. Furthermore the inductive ballast may be formed by windings of the autotransformer and the series circuit including the contacts of the switch 11 may have one end connected to a tapping on the autotransformer.