Circuit breaker auxiliary contacts

A great topic!

Auxiliary contacts are an important feature of circuit breakers, and they play a crucial role in many electrical systems. Here's a detailed overview:

What are auxiliary contacts?

Auxiliary contacts are additional contacts that are built into a circuit breaker, in addition to the main contacts that interrupt the circuit. These contacts are designed to provide a signal or a control function when the circuit breaker is in a specific state, such as:

  1. Closed: The circuit breaker is in the "on" position, and the main contacts are closed.
  2. Tripped: The circuit breaker has opened due to an overcurrent or other fault, and the main contacts are open.
  3. Reset: The circuit breaker has been manually reset or has automatically reset after a fault has been cleared.

Types of auxiliary contacts

There are several types of auxiliary contacts, including:

  1. Normally Open (NO) contacts: These contacts are open when the circuit breaker is in the "on" position and close when the circuit breaker trips.
  2. Normally Closed (NC) contacts: These contacts are closed when the circuit breaker is in the "on" position and open when the circuit breaker trips.
  3. Changeover (CO) contacts: These contacts are normally open and close when the circuit breaker trips, then reopen when the circuit breaker resets.

Applications of auxiliary contacts

Auxiliary contacts are used in a wide range of applications, including:

  1. Monitoring and control: Auxiliary contacts can be used to monitor the status of a circuit breaker and control other devices or systems in response to changes in the circuit breaker's state.
  2. Alarm and indication: Auxiliary contacts can be used to trigger alarms or indicators when a circuit breaker trips or resets.
  3. Interlocking: Auxiliary contacts can be used to prevent unauthorized access to a circuit or to ensure that a circuit is not energized until a specific condition is met.
  4. Power switching: Auxiliary contacts can be used to switch power to other devices or systems in response to changes in the circuit breaker's state.

Design considerations

When designing a circuit breaker with auxiliary contacts, several factors must be considered, including:

  1. Contact rating: The auxiliary contacts must be rated for the same current and voltage as the main contacts.
  2. Contact material: The auxiliary contacts must be made of a material that can withstand the electrical and mechanical stresses of the circuit breaker.
  3. Contact configuration: The auxiliary contacts must be configured to provide the desired function and to ensure reliable operation.
  4. Mounting and wiring: The auxiliary contacts must be securely mounted and wired to ensure reliable operation and to prevent damage to the circuit breaker.

In summary, auxiliary contacts are an essential feature of circuit breakers, providing a way to monitor and control the status of the circuit breaker and to trigger alarms, indicators, or other devices in response to changes in the circuit breaker's state.