Relays and Circuit Breakers

Relays and circuit breakers are both electrical devices involved in the transmission of electrical signals. Despite this, they have many distinct differences. This blog will break down the differences between relays and circuit breakers.

A Relay is a switch that operates as a sensing and controlling device which makes and closes contacts electronically or electromechanically. They are also used as protective devices which sense the fault signal and send it to the circuit breaker where the circuit is either made or broken, depending on the information transmitted by the relay. Circuit breakers are controlling protective devices which make or break a circuit manually or automatically during normal or fault conditions such as short circuit or over-current. Within a circuit breaker, the relay senses the fault and sends the signal to the electromechanical switch, which opens the contacts to protect the circuit. Here are the primary differences between the two devices:


A Circuit Breaker is the combination of an internal electromechanical switch and a relay mechanism which interrupts the circuit during short circuit or overload. In a relay, a coil within the relay creates an electromagnetic field while the solenoid armature opens and closes the contacts when the coil is energized.


Circuit breakers provide interruption only, hence their name ‘breaker.’ fault detection is performed by a relay within the circuit breaker. Relays are switching devices that open and close their contacts electronically or electromechanically.

Working Principle

A circuit breaker automatically breaks the connected circuit when it receives an error signal sensed by a relay within the circuit breaker. Relays act as switching and sensing devices and send the fault signal to the circuit breaker as it occurs within the power system.

Voltage Level

Circuit breakers can operate on both low and high powers and voltage levels, while relays operate on low power and voltage input signals with guaranteed isolation during operation.

Control of a Circuit

Like a switch, circuit breakers can control just one circuit. Relays are able to select or control one of a number of circuits.

Use as an Amplifier

Circuit breakers cannot be used as an amplifier, they only receive signals from a relay and operate based on that signal. Relays can act as an amplifier. They are able to turn one signal into many, or turn low-voltage signals into high-voltage signals.


Circuit breakers are used in low and high current devices, including home electrical wiring, industrial equipment, electrical machines, power plants, and electricity sharing systems. Relays are used to isolate low voltage circuits from high voltage circuits, control multiple circuits, control heavy electrical loads in microprocessors, protect overload relay motors, as well as being used in automatic changeover switching.


April 29, 2022
December 6, 2021

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