Protective device for induction heating apparatus

Claim 1

A protective device for induction heating apparatus comprising: a specific heating element for holding a substance to be cooked, an excitor for induction heating the specific heating element, means for applying an operating voltage to the excitor, a power switch for turning on the excitor, means for delaying the application of the operating voltage to the excitor for a predetermined time after the turning on of the power switch, means for detecting immediately after the turning on of the power switch and thereafter the presence of a heating element other than the specific heating element, the absence of the specific heating element or any other heating element or an undesirably high temperature of the specific heating element, means for preventing the application of operating voltage to the excitor in response to detection of the presence of a heating element other than the specific heating element, the absence of the specific heating element or any other heating element or an undesirably high temperature of the specific heating element, the excitor comprising a first series circuit of a group of excitation windings and a capacitor, the detecting device comprising a second series circuit of a mimic winding and a capacitor, the second series circuit being connected in parallel to the first series circuit to pass current having substantially the same phase as that of the current passing through the first series circuit during normal operation, and means for applying a voltage lower than the operating voltage to the excitor during the predetermined time for detecting the presence of a heating element other than the specific heating element, the absence of the specific heating element or any other heating element or an undesirably high temperature of the specific heating element.