Safety Relays

A safety relay is best described as an electrical switch which can open and close by being under the control of a different electrical circuit. The first safety relay was invented by a man called Joseph Henry in 1835 and in its original form operated by the use of electromagnets. A safety relay can control the output of a circuit and can be considered to be a kind of electrical amplifier. A simple safety relay or electromagnet relay, consists of coiled wire surrounding a soft iron core. This provides a low reluctance path for magnetic flux. An armature is hinged to the core and linked to a moving contact. When the safety relay is de-energised there is a gap in the magnetic circuit. An electric current is passed through the coil and the movement of the contact is broken.