GB542451A - Improvements in electric valve control circuits - Google Patents

Abstract

542,451. Control systems for resistance welding &c. BRITISH THOMSON-HOUSTON CO., Ltd. Aug. 16, 1940, No. 13120. Convention date, Aug. 17, 1939. Addition to 535,933. [Class 38 (iv)] Thermionic control.-The pre-charging of a condenser 7 in a series resonant circuit for power factor improvement according to the parent Specification has the pre-charging voltage adjusted in accordance with the setting of the loadcontrol means. As shown a phase-shifting transformer 32 determining the ignition timing of the valves 8, 9 is coupled with a variable ratio transformer 24 supplying the pre-charging voltage through a rectifier 25. The load current may also be adjusted by coupling the switch 15, changing the series capacity, to a tapping switch on the primary winding of the transformer 5 or by varying a resistance in the primary circuit. The transformer 24 may be supplied from a separate source or from the load circuit as by connection to the terminals of the valves 8, 9. Specification 514,004 is referred to. The Specification as open to inspection under Sect. 91 comprises also the subject-matter of the parent Specification and (1) a three-phase electrdde furnace transformer coupled to a supply circuit with a resonance condenser in series with each electrode and (2) a resistance welding circuit resonance condenser in series with the welding transformer with load control means comprising an asynchronously driven commutator. This subject-matter does not appear in the Specification as accepted.