Radio-Frequency Heating

Abstract

AT an informal meeting of the Institution of Electrical Engineers held in London on January 24, the industrial applications of radio-frequency methods of heating were discussed, and the opening speaker was Mr. N. R. Bligh. The two main fields of application were eddy current heating and capacitance current heating. A third heating field was where the use of radio-frequency currents was only involved because such currents could be led into the charge through small capacitances; the actual heating process, however, was of the resistance heating class. The valve generator appears to be capable of generating all the power yet required for any application, even up to the highest frequencies of some hundreds of megacycles, and Mr. Bligh suggested that the only power rating which should be stated for a radio-frequency generator is its power output into its optimum resistance load, though for convenience the volt-ampere rating might also be given. The self-oscillator was regarded as the simplest form of generator, and up to a few hundred watts, envelope valves could be used, but beyond this, external anode valves were preferable.