The picture above shows a 3000 series Relay, which is one of the standard BPO types.
The relay consists of a coil, mounted on a yoke. Fitted to the yoke are the contact sets and finally an armature is pivoted on the front of the yoke, held in place by a locating screw or clip.
The coil is energised and this attracts the armature, which pivots on the yoke, operating the contact sets. A simple device, but one that has hundreds of variations, due to different contact sets, coil types and armatures.
The residual stud is non-conductive and prevents the armature from remaining closed due to residual magnetism.
Last revised: November 28, 2010