All Types of Relay Symbol and Diagram


The relay is an electrically operated switch. It has three sets of terminals - input terminals, output terminals, and control input terminals. The main function of a relay is to make or break an electrical or electronic circuit according to the input control signal. 
Generally, two types of contacts are there in a relay - closed contact and open contact. In normal condition, the closed contact remains closed and pass electric current whereas the open contact remains open. But when a control signal is applied to the coil of the relay, its closed contact becomes open and open contacts become closed.

All Types of Relay Symbol and Diagram, symbol of relay



There are so many different types of relay available according to their function, construction, terminals, etc. Here you can see the list of different types of relay as below.

  • Electromagnetic Relay
  • Thermal Overload Relay
  • SPST Relay
  • SPDT Relay
  • DPST Relay
  • DPDT Relay
  • Double Coil Latching Relay
  • Overcurrent Relay
  • Differential Relay
  • Pulse Relay
  • On/off time delay relay
  • Remanence Relay
  • No Volt Relay
  • AC Relay
  • DC Relay
  • Polarized Relay
  • Distance Relay or Impedance Relay




The electromagnetic relay has a coil and contacts. When a power supply applied to that coils it becomes an electromagnet and attracts the contacts to close or open. Here, you can see the symbol of the electromagnetic relay.

Electromagnetic Relay Symbol, symbol of Electromagnetic Relay



Thermal Overload Relay does not have any magnetic coil. It has a bi-metallic strip. According to the magnitude of the flow of current, the bi-metallic strip get expands and causes the auxiliary contacts to get open or closed. Here, you can see the symbol of the Thermal Overload Relay.

Thermal Overload Relay Symbol, symbol of Thermal Overload Relay



SPST or Single Pole Single Throw Relay has only one contact either NO or NC. It has a total of four terminals including the coil terminals. Here, you can see the symbol of SPST Relay.

SPST Relay Symbol, single pole single throw





SPDT Relay or Single Pole Double Throw relay has a total of five terminals. Two for the magnetic coil and three for the contacts. In the contact mechanism, it has one common terminal, one NO terminal, and one NC terminal. Here, you can see the symbol of SPDT Relay.

SPDT Relay Symbol, single pole double throw



DPST relay or Double Pole Single Throw relay is the parallel combination of two SPST relays with a single magnetic coil. Including the coil terminals, it has a total of six terminals. Here, you can see the symbol of DPST Relay.

DPST Relay Symbol, Double pole single throw



DPDT Relay or Double Pole Double Throw Relay is the parallel combination of two SPDT relays with single magnetic coils. Including the coil terminals, it has a total of eight terminals. Here, you can see the symbol of the DPDT Relay.

DPDT Relay Symbol, Double Pole Double Throw





Double coil latching relays are constructed with two magnetic coils. Most of the latching relays are DPDT types and they used the latching principle for their operation. Here, you can see the symbol of the latching relay.

Double Coil latching Relay Symbol



As its name suggests the Overcurrent relay actuates when overcurrent flows through it. It allows the continuous flow of current through it and operates when the flow of current exceeds a limit. Here, you can see the symbol of overcurrent relay.

Overcurrent Relay Symbol



Differential Relay actuates when there any difference occurs in two same electrical quantity. Generally, it has two magnetic coils connected in such a way that when there any difference occurs in the flow of current in that two coils, the differential relay will operate. Here, you can see the symbol of the differential relay.

Differential Relay Symbol



Pulse Relay is mainly designed to operate with pulse signals. Pulse relay is used where frequently switch ON/OFF required for a defined time. Here, you can see the symbol of Pulse Relay.

Pulse Relay Symbol





On/Off Time Delay Relay has a time adjustment mechanism. It does not get off or on instantly. It always got on or off after the predefined delay time. Here, you can see the symbol of the Time Delay Relay.

Time Delay Relay symbol



Remanence Relay is designed with a Set and Reset mechanism. We can easily set or reset it. Remanence relay available in both AC and DC categories. Here, you can see the symbol of Remanence Relay.

Remanence Relay Symbol



No Volt Relay or NVR is designed to operate with a very low voltage. Generally, the under-voltage relay is also called a no-volt relay. It actuate when a low voltage applied across its coil terminal. Here, you can see the symbol of No Volt Relay.

No Volt Relay Symbol



AC and DC relays are different according to the type of power supply they need to operate. AC and DC relay coils have different internal resistance and different no. of turns.

AC Relay Symbol



Polarized Relays are constructed with a permanent magnet and a magnetic coil. It supplements the magnetic flux of the electromagnetic coil. Here, you can see the symbol of Polarized Relay.

Polarized Relay Symbol





Distance Relay is also known as Impedance Relay. It mainly used in electrical transmission lines. It actuates depending upon the distance of fault on the transmission line. Distance relay is used to find the location of the fault in the transmission line. It calculates the impedance to find out the distance of fault. Here, you can see the symbol of Distance or Impedance Relay.

Distance or Impedance Relay Symbol

Solid State Relay

Solid State Relay (SSR) symbol

Stepping Relay

Stepping Relay Symbol




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All Types of Relay Symbol and Diagram All Types of Relay Symbol and Diagram Reviewed by Author on 6/29/2021 Rating: 5
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