General Electric Company

Carl E Wellman, Jr

Richard E Hornung

Ronald J Doerr

A ground fault interrupter type device for protecting an electrical load device such as a range which has conductors supplied from a power source including overcurrent interruption means for interrupting the power source when a predetermined current threshold is exceeded. The electrical load device is subject to a first class of failure characterized by excessive current flow between at least one of the conductors and a ground reference point, with circuit current remaining at or below the predetermined current threshold; and to a second class of failure characterized by current through at least one of the conductors being above the predetermined current threshold. Failures of the second class include ground fault failures. In order to reduce the current interruption capability requirement for the ground fault interrupter device, there is included a means for preventing conductor interruption thereby in the event a failure of the second class occurs. Accordingly, the current-interrupting capability is at least as high as the predetermined current threshold but less than the maximum current which may flow during a failure of the second class. In the illustrated embodiments, the means for preventing conductor interruption in the event a failure of the second class occurs is a time delay which delays the activation of the ground fault interrupter for an interval sufficient to allow the overcurrent interruption means to interrupt the power source in the event a failure of the second class occurs.

Ground fault protective system requiring reduced current-interrupting

Solid-state circuitry is provided for an electrical thermometer for monitoring the interior temperature of food being cooked. A temperature sensing thermistor located in the tip of a probe, adapted to be partially inserted in food being cooked so as to monitor the interior temperature, is combined in circuit with a programmable unijunction transistor (PUT), used as a bridge threshold detector, an NPN transistor-diode load current switch and a buzzer alarm coil such that upon the reaching of a preset temperature within the food, the buzzer alarm is actuated. The self-heat of the thermistor probe provides a latching effect ensuring the continued firing of the PUT with the resultant smooth operation of the buzzer alarm. A resistor is combined in circuit to allow a slight back current to flow through the buzzer coil, thereby allowing the use of a buzzer alarm with a fairly non-critical air gap.

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Louisville, KY, United States of America

Carl E Wellman, Jr