Tocco, Inc.

Jonathan W Alexander

George D Pfaffmann

George M Mucha

Richard H McKelvey

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.

Method of monitoring induction heating cycle

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 said inductor, as the voltage varies during said 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.

A power inverter particularly suited for use in applications requiring serially inductively heating workpieces in a predetermined manner, having a main inverter and an auxiliary starting inverter, in an arrangement in which the starting inverter is selectively applied and removed from the load in predetermined timed relationship with the application of the main inverter across the load, and providing a decrease in the inherent instability of the main inverter operation through an increase in the apparent Q of the load, while adjusting the output of the starting inverter to a value greater than the instability level of the main inverter.

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Boaz, AL, United States of America

Jonathan W Alexander