Method of monitoring induction heating cycle

摘要

A method of monitoring a heating cycle of an induction heating system wherein an inductor encircles a metal workpiece and an alternating current is applied through the inductor from a power supply during the heating cycle. This method comprising the steps of generating an analog signal representative of the voltage across the inductor, as the voltage varies during the heating cycle by changes in the electromagnetic characteristics of the workpiece as the workpiece is being heated; digitizing the voltage representative analog signal; creating a trace of the digitized voltage representative analog signal, with the trace being indicative of the electromagnetic characteristic of the workpiece as sensed by the inductor voltage during the heating cycle; and, comparing the created trace with a preselected pattern. This method can be performed with the workpiece moving through the inductor during said heating cycle and when the heating cycle includes a number of sub-cycles when the power supply is energizing the inductor separated by periods when the power supply is not energizing the inductor.