GB632271A - Relays - Google Patents

Abstract

632,271. Electromagnetic relays. GENERAL RAILWAY SIGNAL CO. Sept. 25, 1947, No. 26047. Convention date, Sept. 27, 1946. [Class 38(v)] A polarized relay which will respond to current in one direction but will be unaffected by current in the other direction even though this is considerably greater comprises windings on two parallel cores 24, 25 which are connected at their R.H. end by a yoke 43 and at their L.H. end by the permanent magnets PM1 and PM2 and by a magnetic shunt 32 having a portion 33 of reduced cross-section. The armature 44 is at the L.H. end and is biassed by an adjustable spring 48 away from the poles 21, 22. The flux from the permanent magnets has three paths, through the armature, yoke and shunt respectively. When the windings are energized with current of the right direction, the flux due to the windings supports the permanent flux through the armature and little is diverted through the shunt 32 owing to the latter being saturated. The armature is therefore attracted. When the current is cut off the spring 48 restores the armature. A strong reverse current does not cause attraction of the armature because it opposes the flux in the shunt and would have to do this to an extent to saturate the shunt in the reverse direction before sufficient flux would be diverted to the armature to reverse its flux sufficiently to cause attraction. A slotted shunt produces this effect most readily.