PROTECTIVE CIRCUIT ARRANGEMENT FOR A SHEATHED HEATING ELEMENT

摘要

PROTECTIVE CIRCUIT ARRANGEMENT FOR SHEATHED HEATING ELEMENT A protective circuit arrangement for sheathed heating elements which interrupts ground fault conditions by effectively decoupling the power line from the heating element regardless of the polarity of the power supply connections. A fusible link couples each side of the heating element to the power supply. A normally open switch responsive to current in the ground path switches a relatively low resistance shunt current path across the heating element when the ground current exceeds a predetermined threshold level. Closure of the shunt path enables sufficient current to flow in the power supply lines to actuate the fusible links. Circuit parameters are selected such that the current in the fusible link coupled to the hot power line is sufficiently greater than that in the fusible link coupled to the neutral line to cause the hot power line fusible link to be actuated first, thereby interrupting the fault condition and decoupling the hot power line from the heating element.