초록 ▼

A heating panel has a substrate with a resistive heating material disposed thereon. The substrate can be metal with an insulating layer disposed between the substrate and the heating layer. Alternatively, the substrate can be glass ceramic. The heating layer has electrodes on opposite edges connecte

A heating panel has a substrate with a resistive heating material disposed thereon. The substrate can be metal with an insulating layer disposed between the substrate and the heating layer. Alternatively, the substrate can be glass ceramic. The heating layer has electrodes on opposite edges connected to different phases of a multiphase power source. Another electrode on the heating layer can be connected to a neutral of the power source. Capacitive currents caused in the substrate or a metal object on the substrate by the different phases cancel each other. Thus, leakage current through a conductor connected between the substrate and ground is minimized. The heating panel can be adapted for two phase or three phase systems. Power to the panels is controlled by solid state switches or relays. Zero crossing drivers sense supply voltages and operate the switches to balance currents in the panels. The zero crossing driver operates the corresponding switch or switches to turn the power on or off at a zero crossing of the voltage.

대표청구항 ▼

[ What is claimed is:] [31.] An oven comprising:an enclosure defining a generally parallelepipedic cooking cavity having five walls closed by a door;a heating panel disposed on at least one of walls and the door, the heating panel comprising:a heating layer of electrically resistive sheet material;a

[ What is claimed is:] [31.] An oven comprising:an enclosure defining a generally parallelepipedic cooking cavity having five walls closed by a door;a heating panel disposed on at least one of walls and the door, the heating panel comprising:a heating layer of electrically resistive sheet material;a substrate of electrically conductive sheet material;an electrically insulating material substantially enclosing the substrate to define inner and outer insulating layers, said outer insulating layer being disposed between the heating layer and the substrate and said inner insulating layer facing the cavity;a first electrode attached along an edge of the heating layer and adapted for being electrically connected to one phase of a multiphase power source;a second electrode attached along an edge of the heating layer opposite from the first electrode and adapted for being electrically connected to a second phase of the multiphase power source;a control input;first and second switches each connected to the respective electrodes and adapted fcr being electrically connected to different phases of a multiphase power source to control power to the electrodes; anda zero crossing driver connected to the control input, connected to sense voltage in one of the phases, and connected to operate at least one of the switches, wherein the zero crossing driver is enabled by the control input to operate the switch at a zero crossing of the voltage in the one phase.