GB251758A - Improvements in or relating to high frequency electric induction furnaces - Google Patents

Abstract

251,758. Burch, C. R., Davis, N. R., and Metropolitan-Vickers Electrical Co., Ltd. April 18, 1925. Induction furnaces. - In a high frequency induction furnace wherein the inductor consists of a tube through which a cooling fluid is circulated, the inflow and outflow of the latter are arranged at equipotential points. In Fig. 1 the inductor 10 comprises a copper tube of square section which is doubled back on itself and then wound to spiral form. The inlet 13 and outlet 14 of the tube are connected to earth. If the fluid is a good conductor and the supply thereof is earthed a direct earth connection to the metallic conductor is unnecessary. The point 12 on the conductor is connected through a blocking condenser 15 to the anode of a thermionic valve 16 coupled to a generator 18 through a choke coil 17. The valve may be separately excited or the grid circuit may be coupled to the anode circuit. A condenser 20 is shunted across the inductor 10 to tune the inductor circuit. The valve cathode and condenser are connected to earth or to a common connection together with the inflow and outflow end of the inductor. In Fig. 2 the tube is wound in two different directions to form an inductor 10 and a choking coil 21. In Fig. 3 the inductor 10 consists of two oppositely wound coils. A switch 19 in the supply circuit is arranged to be responsive to the rate of flow of the cooling fluid or the temperature thereof. The cooling fluid flows through a pipe 40, Fig. 4, having a throat 41 between which and the main part of the tube is fitted a U-tube 43 containing mercury and having platinum contacts 44, 45 connected to a battery 47 and relay 46. The contacts of the relay are arranged in circuit with a battery and the operating coil of the switch 19. Temperature control is effected by a thermometer with platinum contacts.