Difference between Relay and Circuit Breaker

By Jaxson

Main Difference

These both are active electrical devices to protect the electrical circuits. But observing them acutely there are many differences between them. A circuit breaker is a strong automatically controlled electrically powered switch built to safeguard an electric circuit from destruction brought on by an excess of voltage or short circuit. Its fundamental characteristic is to recognize a fault condition and break up the current flow. The circuit breaker is mainly used for protecting electrical circuits from the overflow of current so that the circuit is protected from damage. The circuit breaker has a different function from the fuse and relay, it also serve the same purpose as fuse does but fuse protects the circuit only once,  after its function it is burnt down and replaced but circuit breaker can be used many times, either automatically or manually. On comparison with the relay,  it is  an electrically handled switch, most of the relays are used when a circuit is operated  through  a low-power signal, or exactly where a number of circuits need to be operated through a single signal. most of the times switch is operated mechanically by a relay. Relays are generally switched that open and shut circuits  electronically or electro-mechanically. They manage one electric powered circuit by closing and opening contacts in another circuit. When a  contact of the relay  is open up, the relay is not stimulated.


Relays are similar to handy remote control switches and, therefore, are employed in several purposes due to their comparative simplicity, endurance, and tested substantial dependability. Relays are utilized in an extensive range of applications throughout the industry, for example in digital computers, telephone exchanges, and automation systems. Tremendously exceptional relays are employed to safeguard electrical power systems against issues and power shutdowns, in addition, to regulating and manage the distribution and generation of  power. At houses, relays are utilized in refrigerators, washing machines, dishwashers, and heating and air conditioning controls, many more appliances are also using relays for protecting circuits. Even though relays are usually connected with electric powered circuits, there are lots of other kinds, for example, pneumatic and hydraulic . some important parameters on the basis of which relays are selected  are their  characteristics, specifications and the demand of the circuit. mainly, they are selected on the  basis of  load types, coil options, contacts, and arrangements. Maximum allowable voltage and current through the circuit is handled and controlled through the relay. Mainly  loads are classified into four main categories

  • Resistive load
  • Inductive loads
  • AC or DC
  • High or Low Inrush.

These four types of loads play a vital role in the selection of the relay. Some types of relays are  Latching relay, Reed relay, Mercury-wetted relay, Mercury relay, Polarized relay, Machine tool relay, Coaxial relay, Time delay relay, a heavy duty contractor relay, Solid-state relay, A solid state relay or SSR, Solid state contractor relay, Buchholz relay, Force-guided contacts relay, Overload protection relay, Vacuum relays, Safety relays, Multi-voltage relays.

Circuit Breaker

Circuit breakers are available in different sizes, dimensions, and measurements from tiny devices that safeguard an individual household equipment up to massive switch-gear made to guard high voltage circuits serving a complete town. All circuit breaker devices currently have typical characteristics within their functioning. Despite the fact that specifics differ considerably with regards to the voltage class, current rating, and kind of the circuit breaker.

The circuit breaker should identify a problem and fault condition; in reduced voltage circuit breakers normally, this is completed inside the circuit breaker box. Circuit breakers with regard to massive currents or higher voltages are often organized with shielding relay pilot equipment to perfect sense a fault condition and also to function the particular trip opening feature. The particular trip solenoid which produces a latch is generally stimulated with an independent battery, even though some high voltage circuit breakers are generally self-contained along with current transformers, shielding relays as well as an interior manage power supply. When a fault is sensed by the circuit breaker, contacts of the circuit breaker operate to break the connection of the fault area with the circuit and  break up the circuit; several mechanically-stored power  included inside the circuit breaker is utilized to split up the particular connections, however, some of the power needed could be extracted from the fault current itself. Tiny circuit breakers could be operated by hand, more substantial models possess solenoids in order to trip the process, and electric powered motors to regenerate energy to the springs.The circuit breaker connections should have the load current without having an extreme heating problem, and should definitely endure the temperature of the arc created whenever interruption is in  the circuit. Connections are constructed with copper or copper metals, silver alloys along with other extremely conductive products. Support lifetime of the connections is restricted through the breakdown of contact substance because of arcing whilst interrupting the current in the circuit. Some circuits are usually not used when the connections are deteriorated like in molded-case and Miniature circuit breakers  however power circuit breakers and high-voltage circuit breakers currently have changeable connections. during short circuits, circuit breakers play a vital role and protect the circuit by heating up or damaging. Usually, circuit breakers have standard current ratings, specific trip settings and time delay operations (usually less than 100 milliseconds). Some major types of circuit breakers are listed below

  • Low-voltage circuit breakers
  • Thermal magnetic circuit breakers
  • Common trip breakers
  • Medium-voltage circuit breakers
  • High-voltage circuit breakers
  • Sulphur hexa-fluoride (SF6) high-voltage circuit breakers
  • Disconnecting circuit breaker (DCB)
  • carbon dioxide (CO2) high-voltage circuit breakers
  • Magnetic circuit breakers

Key Differences

  • Relay can control current whereas circuit breaker just senses it.
  • Relay is directional and non-directional whereas circuit breaker is non-directional.
  • Relay is controlling device whereas circuit breaker is switching device.
  • Relay is controlled by low power signal and guarantees full electrical isolation whereas switch is triggered  and current flow is disrupted in circuit breaker.
  • A relay can certainly be regarded as an electric amplifier for discrete signals but it’s not the case in circuit breakers.
  • The relay can operate one or more circuits at a time where as circuit breakers are used one per circuit.
  • circuit breakers are automatic on load devices while relay operates on low power signals.
  • The relay is utilized pertaining to managing a circuit with isolation involving control circuit and also the controlled circuit whereas Circuit breaker is commonly employed with regard to disconnecting or separating a circuit from your power supply  higher.

Video Explanation

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