Abstract: In an electromagnetic induction heating apparatus, a cooking vessel made of a nonmagnetic metal, which has conventionally been incapable of magnetic inducting heating, is provided adjacent a heating coil which applies an alternating field with a high-frequency of at least 50 kHz. An inverter circuit for supplying the heating coil with a high-frequency current operates in response to an output signal from a detector which automatically detects the magnetic characteristics of the metallic material of the cooking vessel. As the high-frequency magnetic field is applied, a skin effect is produced within the metallic material of the vessel, so that the impedance for the magnetic field of the vessel is substantially fixed without regard to the wall thickness of the vessel.

Abstract: A microwave heating apparatus comprises a solid state oscillating circuit, a pre-amplifier module for amplifying the output of the oscillating circuit, a plurality of amplifier modules for amplifying the output of the pre-amplifier module, a first power supply source for energizing the solid state oscillating circuit and a second power supply source for energizing all of the amplifier modules. Such an apparatus further comprises a delay circuit for activating the first power supply source after the second power supply source has been activated and the amplifier modules have been in a stable state.