GB463097A - Improvements in and relating to induction furnaces - Google Patents

Abstract

463,097. Supply systems for highfrequency apparatus; converting. AKT.- GES. BROWN, BOVERI, & CIE. Feb. 13, 1936, No. 4437. Convention date, Feb. 13, 1935. [Classes 38 (ii) and 38 (iv)] A high frequency induction furnace is supplied from a D.C. source through electric discharge current converters having extinguishing grids of the type described in Specification 430,915, [Group XL], by which the anode currents are started and stopped at intervals depending upon the frequency of the resonant furnace circuit the capacity of which is constant, the frequency being dependent upon the state of the furnace charge. Current is supplied from the D.C. source u to the cathode m and the anodes b of an inverter, the cathodes being also connected to the middle of the primary of a transformer f. The secondary of this transformer is in the resonant circuit including the induction furnace winding g and the condenser i. The inverter is ignited and extinguished in dependence upon the resonant circuit by grids c connected to a high frequency machine o for starting and later, by a coil r coupled with the furnace winding when the machine o is disconnected by a switch s. The inverter thus energizes the furnace through the transformer f at a frequency which varies with variations of the natural frequency of the resonant circuit. Ignition electrodes k may be provided. In one modification, the grid voltage is associated with the resonant circuit through an additional winding on the transformer f, and in a further modification through a resistance across the condenser i. Reference has been directed by the Comptroller to Specification 402,791.