An Automatic Controller for Radiofrequency Induction-Heating Units

Abstract

A simple, rugged, and adaptable device for regulating the power provided by an industrial rf generator for induction heating is described. An rf voltage picked up by a small coil near the work coil is rectified, opposed by an adjustable dc reference voltage, and the difference‐voltage fed to a commercial chopper‐type dc amplifier and servo motor. The motor drives the power‐controlling element of the generator in such a direction as to reduce the error signal to zero. Regulation of temperature within ±½ degree at 1000°C has been achieved where system is not disturbed in any way.