GB858248A - Improvements in or relating to thermally-operated protective devices for polyphase circuits - Google Patents

Abstract

858,248. Protective cut-out arrangements; thermal switches. TELEMECANIQUE ELECTRIQUE. April 16, 1958 [May 3, 1957], No. 12170/58. Class 38 (5). An unbalance and overload polyphase protective device has parallel bimetallic members 1a . . . 1c spaced in a common plane and flat transverse elements 6 each having a portion extending between and pivoted to a pair of adjacent bimetallic members. Each element 6 has arms 6b which engage arms 5 secured to a shaft 2 carrying a moving contact 3 co-operating with an adjustable fixed contact 4. Under balanced overload conditions in which the members 1a . . . 1c are heated equally by the phase currents flowing through them or adjacent heater elements, the bimetallic members deflect equally and move the elements 6 bodily to open the contacts 3, 4. In the event of unbalance, the unequal deflections of the bimetallic members causes one or both of the elements 6 to tilt and turn the arms 5 to open the contacts. The elements 6 are supported in, and guided by, slots 7a in insulating partitions 7 extending between the bimetallic members. The pivotal connections between the bimetallic members and the elements 6 may be provided by recesses in the elements 6 shaped as shown, or by parallelsided recesses in the elements 6 which co-operate with semi-cylindrical bearing-elements on the bimetallic members, Fig. 5 (not shown). Alternatively, each element 6 may be pivoted to one bimetallic member by a pivot-pin and to the other by means of a recess.