EM relay for coupling to semiconductor relay - receives mercury globules in trough forming contacts with halves of toroidal magnetic circuit connected static relay

摘要

The relay has an associated electromagnetic relay connected in parallel to shunt current past the Triac and avoid excessive heating of the latter. The electromagnet has an energising coil formed by part of the relay load circuit and an armature (4) formed by a segment of a toroidal magnetic circuit (2) split by an electrically insulating magnetically conductive spacer diametrically opposite the armature. The opposing faces of the toroid and armature receive mercury globules in troughs forming the relay contact with the respective toroid halves electrically connected across the triac. The speed of the electromagnetic relay is such that the armature closes with the toroid halves over less than 45 degrees of the load a.c. once the triac is fired to shunt current past the latter, and opens before the load a.c. reaches its crossover point.