Westinghouse Electric Corporation

William E Frank

John Rosa

Chuck F Der

Erwin A Billman

A two-pole inverter bridge has an inductor mounted between the two controlled switches in each pole and a resonant load is connected across the poles between ends of the inductors which are similarly situated relative to the terminals. In each pole one antiparallel circuit includes an auxiliary controlled switch and another antiparallel circuit includes only a diode. Fault protection is provided with an auxiliary source mounted between opposite ends of the inductors for applying reverse bias to the controlled switches of the poles whenever a fault in the inverter is detected.

High frequency inverter circuit for melting and induction heating

A solid state radio frequency high power generator for induction heating applications uses MOSFET devices controlled at radio frequency by a current loop which is automatically corrected against the possible occurrence of a leading phase shift by a voltage-current phase shift detection loop which responds to digital signals corrected against inherent time delays.

Solid state radio frequency power generator

Coil current loading the induction coils of an induction heating apparatus is directly sensed at the input from the tank circuit and the derived feedback current signal is used to control the power supply to the tank circuit be reference to a signal provided manually or automatically under process control. A voltage feedback signal is derived with a transformer from the input to the tank circuit for providing an input to a voltage limiter operative on the current controller when the voltage to the tank circuit exceeds an acceptable limit. A current limiter overrides the current controller to limit the load current by control of the current controller when the load becomes excessive.

Current control system for an induction heating apparatus

In an induction heating apparatus, direct sensing of the high frequency high power current flowing in the tank circuit to load the induction coils, is obtained with a coil current measuring transformer comprising one of the power current busses leading to the induction coil and a secondary winding of many ampere-turns wound around said one bus. The bus is given a half-loop shape to accommodate the secondary winding. The secondary winding is made of a magnetic core wound with many turns of Litz wire. Cooling tubes are cemented outside the wound secondary with conductive cement to form a heat sink with a circulation of cooling medium through the tube. The cement is divided in two parts separated by gaps to prevent circulation of induced currents. A cooling tube is installed between the core and wound wire to provide an internal heat sink.

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Baltimore, MD, United States of America

William E Frank