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Guilherme Mazui

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What is the Difference Between Relay and Circuit Breaker?

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The main difference between a relay and a circuit breaker lies in their functions and the type of signals they handle. Here are the key differences:

  1. Function: A relay is a switch used for sensing, detecting, and controlling fixed and moving contacts electromagnetically or electrically. It acts as a protective device that alerts the circuit breaker when a fault is detected in the system. On the other hand, a circuit breaker is a non-directional device responsible for acting as a switching device, collecting signals from the relay, and responding accordingly. It is a disconnecting and isolating device that can handle circuits of large amperes of current.
  2. Directionality: A relay can be directional and non-directional, while a circuit breaker is non-directional only.
  3. Signal Provision: A relay only provides signals to the circuit breaker in case of fault conditions. A circuit breaker has both the abilities of making and breaking the circuit automatically, manually, or by remote control.
  4. Amplification: A relay can be used as an amplifier for discrete signals, converting one signal into many, or amplifying a low-voltage signal into a high-voltage signal and vice versa. A circuit breaker cannot act as an amplifier for signals.
  5. Operating Conditions: A relay operates on low power and voltage input signals, while circuit breakers can be used for low as well as high power circuits, as their operation is automatic on load.
  6. Protection: Circuit breakers are typically intended for overcurrent protection, while relays can provide both overcurrent and overvoltage protection.
On this page
  • What is the Difference Between Relay and Circuit Breaker?
  • Comparative Table: Relay vs Circuit Breaker

    • Comparative Table: Relay vs Circuit Breaker

    Here is a table comparing the differences between a relay and a circuit breaker:

    Feature Relay Circuit Breaker
    Type of device Sensing and controlling device, acts as a switch Protective device, acts as a circuit disconnection or isolation
    Operation Senses fault in the power system and sends a message to the circuit breaker Breaks the contact after receiving a signal from the relay
    Uses Switches circuits with small currents Typically used with large currents
    Amplification Can amplify signals (e.g., convert low-voltage to high-voltage) Cannot amplify signals
    Construction Consists of coils that act as electromagnetic fields and an armature that closes and opens the fixed and moving contacts Combination of internal electromechanical switch and relay mechanism
    Directionality Can be directional or non-directional Non-directional
    Fault Detection Senses the fault or specified amount of current and sends the signal to the circuit breaker Detects large changes in current and breaks the circuit automatically, manually, or by remote control

    In summary, a relay is a sensing and controlling device that acts as a switch, while a circuit breaker is a protective device that interrupts an electric circuit to prevent excessive current or short circuits. They serve different purposes and have distinct operational characteristics.

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    Guilherme Mazui

    Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.