GB613007A - Improvements in and relating to lighting circuits for electric discharge lamps - Google Patents

Abstract

613,007. Supply systems for discharge lamps. BRITISH THOMSON-HOUSTON CO., Ltd. Jan. 10, 1944, No. 443. Convention date, Jan. 12, 1943. [Class 38 (iv)] [Also in Group XL (a)] The filaments or heaters of a pair of parallel and reversely connected rectifying discharge lamps or groups thereof are connected in series for starting purposes, the series connection being interrupted by a thermal switch either after the passage of preheating current for a predetermined time or by the flow of " discharge " current. As shown in Fig. 1, paralleled and reversely connected lamps 1, 2 operate in series with similarly connected lamps 3, 4, the four filamentary cathodes being connected in series during starting by normally closed thermal switches 16, 17 having heaters 18, 19 which carry the preheating current and cause the subsequent opening of the switches to interrupt this current and start the discharge. Discharge current then passes through the heaters and maintains the switches open. The filaments or heaters may provide the necessary ballast resistance for the circuit, or an additional choke may be provided for a similar purpose. In the arrangement of Fig. 3, a series of lamps 26-30 are supplied in parallel with a reverse series 31-35 through a choke 24<SP>1</SP>, thermal starting switches 36-40, having heaters 41-45 in series with the lamps 26-30, connecting the cathodes of corresponding lamps of the two series for starting purposes so that all the cathodes are in series. When discharge current is established this passes through the heaters and interrupts the cathode heating circuit.