GB847910A - Improvements in or relating to moving coil electric relay circuits - Google Patents

Abstract

847,910. Electromagnetic relays. SANGAMO WESTON Ltd. Dec. 7, 1956 [Dec. 8, 1955], No. 35311/55. Class 38 (5). A relay circuit arrangement, Fig. 1, comprises a moving coil relay M having an operating winding P, a contact pressure reinforcing winding Q shunted by a variable resistance S, and a moving contact m operating between fixed contacts ml, m2. A mechanical torque may tend to move the contact m towards contact m2. On engagement of the contacts m, m1, due to current of a certain polarity in the winding P, a circuit is completed from an auxiliary supply X, winding Q, the normally closed contact b of attracted armature type relay B, the winding of attracted armature type relay A/2, to the other terminal of the supply X. The winding Q augments the pressure between the contacts so that the contact resistance is lowered A to an extent such that the relay - operates to 2 close its normally open contacts a1 thereb short-circuiting the coil Q and establishing a holding circuit for itself through contacts a1 b. Also, further contacts a2 of the relay A/2 are closed to control a line l1, l2. Thus should vibration separate the contacts m, m1 the arrangement is unaffected and the contacts are not damaged by sparking. On engagement of the contacts m, m2 due to a reduction, or reversal of polarity, in the current in the winding P, a circuit is completed from the supply X, through relay B, winding Q, contacts a1, to the other supply terminal. The winding Q reduces the contact resistance so that relay B operates to open contacts b whereupon relay A/2 releases and the contact m is free to move once more towards contact m1 upon a further change in the current through P. In a modification, Fig. 2, A the relay B is omitted and the relay - is 2 differentially wound having an operating winding a which when energized upon closure of contacts m, m1 closes its contacts a1, a2, and an opposing winding b which when energized upon closure of contacts m, m2 releases the relay A/2. To increase the speed of movement of the contact m from contact m1 to m2 a variable resistance may be connected between the contact m and the negative terminal of the source X (Fig. 3, not shown) whereby a circuit is completed through the winding Q immediately the contact m leaves the contact ml. In a further modification a single winding may replace the two windings P, Q.