What are relays? What are they used for?

Relays are essential to protecting and switching of a number of the control circuits and other electrical components. All the Relays react to voltage or current with the end goal that they open or close the contacts or circuits.

The development of relays was started in 1800s. As a part of the invention of the electrochemical telegraph, the electrolytic relay was found by Samuel in the year 1809. Thereafter, this invention was asserted by the scientist Henry in 1835 in order to make an improvised version of the telegraph and later developed this in the year 1831. Whereas in 1835, Davy absolutely discovered the relay, but the original patent rights were given by Samuel in the year 1840 for the initial invention of the electric relay. The approach of this device appeared the same as a digital amplifier thus replicating the telegraph signal and allowing for longer distance propagation.

Relays have different types, depending on the operating principle and structural features, such as electromagnetic relays, thermal relays, power varied relays, and multi-dimensional relays with varied ratings, sizes, and applications. The types of relays depend on the function for which they are used.

Some of the categories include protective, reclosing, regulating, auxiliary and monitoring relays. Protective relays continuously monitor these parameters: voltage, current, and power; and if these parameters violate set limits they generate an alarm or isolate that particular circuit. These types of relays are used to protect equipment like motors, generators, and transformers, and so on.