Abstract: A getter heating coil assembly producing a focused magnetic field for heating objects in close proximity to the coil assembly. The coil assembly comprises electrical conductors wound on a coil bobbin, the coil bobbin having a central spindle around which the conductors are wound. The wound bobbin is assembled with a magnetic field concentrator, said field concentrator having a central core extending from a base, and a side wall extending from the base to enclose the wound bobbin. The central core of the field concentrator fits within the spindle on the bobbin and extends through it. The coil bobbin remains exposed on one side for emission of focused electromagnetic energy when alternating current is supplied to the coil windings. A button of high magnetic permeability material may be attached to the field concentrator for focusing the emitted electromagnetic energy toward the center of the coil.

Abstract: The present invention relates generally to inductive heating, and more particularly to an apparatus and method for non-contact detection and inductive heating of heat retentive food server warming plates used in institutional food service. The invention provides a non-contact detection and control circuit for an inductive heating apparatus for heating an inductively reactive heat radiating element built into a warming plate. The warming plate employed by the invention has an integral inductively reactive heat radiating element that is brought to a desired heating temperature such as 450.degree. F. In a preferred embodiment, the apparatus is configured like a conventional industrial cook stove and surface. Underneath the surface is a magnetic inductive coil controlled by the invention for inductively heating a reactive ferromagnetic heat radiating element that is placed on the surface.

Abstract: A self-excited solid-state oscillator for supplying a high-power RF inductive load. The oscillator includes at least one MOSFET transistor connected in a self-excited oscillator configuration, an output tuned circuit including an inductive load and a tank circuit connected to the load, the tank circuit having a resonant frequency determined at least in part by the inductance of the load, an RF feedback transformer coupling the tank circuit to the gate of the MOSFET for providing a switching signal to the MOSFET for causing the MOSFET to alternate between the on state and the off state at a frequency equal to the resonant frequency of the tank circuit, and a bias circuit for superimposing a forward bias voltage on the switching signal.