GB553852A - Improvements in and relating to electric valve oscillatory apparatus - Google Patents

Abstract

553,852. Supply systems for high-frequency furnaces. BRITISH THOMSON-HOUSTON CO., Ltd. May 4, 1942, No. 5998. Convention date, May 2, 1941. [Class 38 (iv)] [Also in Group XL] A circuit for converting alternating current of commercial frequency to a higher frequency, comprises an inductance, a capacity and a pair of reversely connected valve means for setting the oscillating circuit formed by the inductance and the capacity in oscillation and supplying a load such as a high frequency furnace. Fig. 1 shows a circuit using a pair of valves 8, 9 using an ionizable medium and having immersion. ignitor control members 12 associated with a condenser 3 and the inductance of the output transformer 5. The excitation circuits 13-16 for the control members 12 are of the kind disclosed in Specification 488,851 and each comprises a discharge tube 23 controlling the application of the potential across a condenser 38 derived by rectification from the mains to a control member under the control of a voltage of adjustable phase derived from the mains through transformer 29. In this way the charge on the condenser is discharged in an oscillatory manner through the tubes 8, 9 at a point in the cycle determined by the phase-shifter 37, Fig. 2, showing the mains frequency A and the discharges ab, cd, ef, gh.