Relay,Different Types of Relays and their Working

Relay and types of relay

A Relay is a switching device and it work is to change the state of an electric circuit or electric current from one state to another. Relays are classified according to their working and structure. Well, known categories include protective, regulating, reclosing, auxiliary and monitoring relays. Protective relays monitor these parameters: current, voltage, and power; and if these parameters violate from mentioned limits they generate an alarm to inform the situation of the circuit.Pin configuration of Relay.

types of relays


Different Types of Relays

Depending on the operating principle relays are of different types such as:

  • electromagnetic relays
  • Solid State Relays
  • Hybrid Relays
  • thermal relays
  • Reed Relays


  •  Electromagnetic Relays

These relays are build with electrical,magnetic tools,and mechanical, and have operating coil and mechanical contacts. So, when the coil gets operated by a  supply system then mechanical contacts gets opened or closed. The kind of provide can be AC or DC.


  •  Solid State Relays

Solid State uses solid state tools to act the switching operation without moving any parts. Because, the control energy needed is very low compared with the output power to be controlled by this relays that results the power gain higher when compared to the electromagnetic relays. These are of different kinds: reed relay coupled SSR,photo-coupled SSR, transformer coupled SSR and so on.


  •  Hybrid Relay

These relays are contain of electromagnetic relays and electronic tools. Generally, the input part contains the electronic circuitry which acts rectification and the other control functions, and the output part involve electromagnetic.


  •  Thermal Relay

These relays are doing increase in the ambient temperature from the limit, directs the contacts to switch from one position to other.These are basically used in motor defense and consist of bimetallic elements such as temperature sensors as well as control elements. Thermal overload relays are the best example of these relays.


  •  Reed Relay

Reed Relays consist a set of magnetic strips which is closed within a glass tube. This reed operates as both an armature and a contact blade.The magnetic field applied to the coil is folded around this tube that makes these reeds motion so that switching work is acts.

Relays are also available with different pin configurations like three pin, four pin and five pin relays. Switching contacts can be DPDT ,DPST, SPDT, and SPST types. Some of the relays are commonly open (NO) kind and the other are commonly closed (NC) kinds.


DC vs AC Relays:

Working of Relay:

Applications of Relay: