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We took a similar 40 A Square D breaker apart to examine the innards: the "thermal unit" in the Xray has a frame (in a 'J' shape) (call it 'J') attached to the wire terminal, and the thick piece (call it 'A'), just beside 'J' going into the "C"-shaped bottom of the 'J', carries a recess into which the long piece from the handle fits. 'A' is springy where is it welded to the end of the 'J' near the terminal, and swings toward 'J' with any force applied. When the thin loop hanging from the 'C' piece, which is bimetallic, starts bending (at its end near the 'C') it bends, and because it is attached to 'A' it pulls on the 'C', which pulls 'A' and the recess away from the handle-piece.
When rapped smartly along the long axis of the body, the cold breaker snaps open.
The connection from the breaking contact on the side near the other terminal, is made by a piece of thick stranded wire welded at both ends. We saw no evidence of any magnetic coils, nor of any mechanism to trip magnetically on theflow through the conductors as arranged.
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