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 of 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 detecting device comprising a first series circuit of a detector winding wound on a detector core for forming a magnetic flux circuit with the heating element to impart a weak attractive force and a capacitor connected to the detector winding and a second series circuit of a mimic winding and a capacitor which is 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 preventing the passage of current to the excitation windings of the excitor for 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.