Three-phase thermal protector

摘要

A three-phase thermal protector includes a hermetic receptacle composed of an elliptic dome-shaped cover having an opening at one end and a header plate having two terminal pins extending through respective apertures formed in it, and a switch assembly mounted in the receptacle. Two fixed contacts are secured to the respective terminal pins. The switch assembly includes a metal operating temperature calibrating plate with one end welded to the cover, a bimetallic thermally responsive element having one end secured to the calibrating plate and the other end having a central dish-shaped portion, and a thermally-responsive-element support to which the supported end of the thermally responsive element is welded. The thermally responsive element carries two movable contacts symmetrical about the center line. The calibrating plate has a push projection pushing the thermally responsive element so that the contact pressure is increased when the calibrating plate is deformed with deformation of the cover for the calibration of the operating temperature. The header plate has a protrusion receiving the thermally responsive element at a position away from its supported end toward the center.