GB599802A - Improvements in or relating to alternating current supply systems for gaseous discharge tubes - Google Patents

Abstract

599,802. Supply systems for space discharge apparatus ; transformers. SOLA ELECTRIC CO. Nov. 10, 1944, No. 22178. Convention date, Nov. 13, 1943. [Classes 38 (ii) and 38 (iv)] An A.C. supply circuit for a gaseous discharge tube 28, Fig. 2, having a high initial breakdown voltage and negative impedance operating characteristic, comprises a transformer 10, Fig. 1, on which the primary 12 is connected to the A.C. source 25, Fig. 2, and the secondary is connected in series with a capacity 30 to the tube 28, the transformer core structure having a high reluctance shunt disposed between the primary and secondary windings to effect relaxation of magnetic coupling between the windings when current flows in the secondary circuit. The transformer core consists of a centre core 11, Fig. 1, having outwardly extending shunt portions 22 separated by small air gaps from oppositely extending portions 18, 19, of upper and lower legs 16 and 17, respectively, of an outer frame, the end portions 14 and 15 of which are notched out to receive the ends of the core 11. Upon energization of the primary winding, a voltage is applied to the tube, substantially equal to the turns ratio voltage of the transformer and sufficient to render the tube conducting. Preferably, the reactance of condenser 30, Fig. 2, relative to the inductance of secondary 13 and the inipedance of the tube 28, is such that series resonance occurs in the secondary circuit when current flows therein, the said current being limited to an optimum value in that the secondary section of the transformer core then operates at maximum flux density and so maintains the current at the said optimum value regardless of variation in the circuit due to the negative resistance characteristic of the tube. The magnetic shunts in the core allow of appreciable variation in primary voltage without substantially affecting the secondary voltage applied to the tube. In a further embodiment, Figs. 3 and 4 (not shown), a pair of secondary windings is associated with a single primary winding, the centre core of which is provided with two sets of outwardly-extending portions co-operating with oppositelyextending portions of the top and bottom legs of the outer frame, to form high reluctance shunts between windings. Each secondary winding supplies a separate discharge tube and each is connected in autotransformer relationship with the single primary. In both the above arrangements, the transformer may comprise separate primary and secondary windings or the secondary winding or windings may be connected in autotransformer relation to the primary winding. Substantially, unity P.F. may be achieved by correlating the capacity reactances of the condenser and tube so that their sum will be equal to the effective inductive reactance of the secondary winding with optimum current in the secondary circuit.