Function of circuit breaker contacts

Circuit breaker contacts are the movable parts that make or break the electrical circuit when the breaker is operated. The primary function of circuit breaker contacts is to:

  1. Make: When the circuit breaker is closed, the contacts come together to establish an electrical path, allowing current to flow through the circuit.
  2. Break: When the circuit breaker is opened, the contacts separate, interrupting the electrical path and stopping the flow of current.

The contacts are designed to perform these functions reliably and safely, with the following characteristics:

  1. Low contact resistance: The contacts should have a low resistance to ensure minimal voltage drop and heat generation.
  2. High current-carrying capacity: The contacts should be able to carry the maximum current rating of the circuit breaker without overheating or arcing.
  3. Low contact wear: The contacts should be designed to minimize wear and tear, ensuring consistent performance over time.
  4. Arc quenching: When the contacts separate, they should be able to extinguish any arcing that may occur, preventing the spread of fire or electrical shock.
  5. Spring return: The contacts should be designed to return to their original position (closed or open) when the circuit breaker is operated, ensuring consistent performance and minimizing wear.

The design of circuit breaker contacts can vary depending on the type of breaker and the application. Common types of contacts include:

  1. Pole and neutral contacts: These contacts are used in single-phase and three-phase circuit breakers and are designed to handle the current flowing between the pole and neutral conductors.
  2. Phase contacts: These contacts are used in three-phase circuit breakers and are designed to handle the current flowing between the phase conductors.
  3. Grounding contacts: These contacts are used in circuit breakers that provide grounding or earthing functions and are designed to handle the current flowing between the grounding conductor and the neutral conductor.
  4. Arc chutes: These contacts are used in circuit breakers that require arc quenching and are designed to extinguish arcing when the contacts separate.

In summary, the function of circuit breaker contacts is to make and break the electrical circuit reliably and safely, while minimizing wear and tear, and ensuring consistent performance over time.