Mercury-Arc Frequency Converter for Induction Heating of Metals

An analysis is presented of the theory of operation of mercury-arc equipment for converting 3-phase power of commercial system frequencies into single-phase power of a frequency of the order of one kc for use in induction heating and melting applications. Mathematical relationships are derived to show the effect of both low -and high-frequency communication and the frequency response of the grid phase angle control on the high-frequency output voltage and regulation. The self-tuning characteristics of the circuit are analyzed and a comparison is made between its response and that of a motor-generator set to changes in the load circuit inductance. Some practical considerations are discussed in connection with the installation and operation of mercury-arc frequency changing equipment of several hundred kilowatts rating for induction melting service.