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Electrical Relay

Updated: Aug 9, 2023

An electrical #relay is a switch. The switch is used to close or open a circuit manually whereas the relay is an electrically operated #switch that is it works automatically with the help of control signals.

When a small current is passed through the coil of the magnetic core, the magnetic field is created that operates the switch and controls larger currents.

Electrical relays are available in different sizes and they can be used in different applications by slightly varying the technology being used.

Symbol of Relay Circuit

Symbol of Relay Circuit
Symbol of Relay Circuit

Basic parts of Relay

The basic parts of the Relay are #Frame, #coil, #armature, and #contacts.

Frame: The components of the relay are supported by a mechanical frame.

Coil: Coil is a wire wound around a metal core that causes an electromagnetic field.

Armature: Armature is a movie part of the relay that opens and closes the contacts and spring brings the armature to the original position.

Contacts: Contacts are the conducting part of a switch that connects or disconnects the circuit.

Types of Relays

Basically, there are two types of Relays. They are #electromechanical Relays and solid-state relays.

Electromechanical Relays:

Electromechanical Relays consist of an electro-magnetic coil along with a movable contact.

When current flows through the coil, the magnetic field is generated that attracts the armature. The mechanical contacts and the armature are attached so that the contact closes when the armature is pulled towards the electromagnet. The armature is brought to its original position by removing the input voltage applied to the coil.

Solid State Relays:

Solid-state relays (#SSR) are the switch that gets on or off according to the input given at its control terminals. It is similar to electromechanical relays but does not have any moving parts which results in a longer operation lifetime. Solid-state relays have a sensor, solid-state switching device, and a coupling mechanism. The sensor responds according to the control signal given as input, the switching device switches the power to load circuitry, and the coupling mechanism enables the control signal to activate the switch without any mechanical parts.

Advantages of Relays:

  • Relays can be used for AC or DC circuits.

  • Relays can be used at high voltages.

  • Relays are able to switch multiple contacts at once.

Disadvantages of Relays:

  • Relays are bulky.

  • Relays cannot switch fast.

  • Relays consume more power and require a large current.

Applications of Relays:

  • Relay has a wide range of applications

  • Relays are used to isolate high voltages from the low voltage in electronic

  • circuits and home appliances.

  • Relays are used in industries for automation processes.

  • Relays are used in railway networks for the purpose of signaling and control.

  • Relays are used for protection, switching, and control in motor control circuits.

  • Relays are used to sense various faults in substations and power distribution centers.


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Written By: Nagapuri Swathi

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Informative and concise! LearnElectronics India always delivers quality content.


Anushka Gupta
Anushka Gupta
Jul 20, 2023

This blog post by Learn Electronics India deserves all the praise it's receiving. The use of real-life applications to explain relay functionality adds an extra dimension to the learning experience. I'll definitely be recommending this article to my fellow electronics enthusiasts.

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