What is Auxiliary Contact and how it works with MCB?
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What is Auxiliary Contact and how it works with MCB?

Views: 69     Author: Site Editor     Publish Time: 2022-07-28      Origin: Site

A miniature circuit breaker can provide much more than current protection, it can also provide remote tripping, status indicator, under-voltage/overvoltage protection, and other features.

What is Auxiliary contact?

Auxiliary contacts (or switches) are supplementary contacts that are added to a circuit to protect the main contact. This accessory allows you to check the status of a Miniature Circuit Breaker or Supplementary Protector from a remote. Simply explained, it aids in remotely determining whether the breaker is open or closed. This device can be used for a variety of purposes other than remote status indication. 

The Miniature Circuit Breaker will turn off the supply to the motor and protect it from the fault if the power circuit has a fault (short-circuit or overload). However, a closer examination of the control circuit reveals that the connections remain closed, supplying electricity to the contactor coil unnecessarily.

What is the function of the auxiliary contact?

When an overload triggers a MCB, the wire to the MCB may burn. If this happens frequently, system may begin to smoke. Auxiliary contact are devices that allow one switch to control another (typically larger) switch.

The auxiliary contact has two sets of low current contacts on either end and a coil with high-power contacts inside. The group of contacts designated as “low voltage” is frequently identified.  

Auxiliary contact, similar to main power contactor coils, which are rated for continuous duty throughout a plant, contain time delay elements that prevent arcing and possible damage if the auxiliary contact opens while the main contactor is still energized.

Auxiliary contact uses:

The main uses of Auxiliary contact are:

  • Auxiliary contact is used to get the feedback of main contact whenever a trip occurs

  • Auxiliary contact keeps your circuit breakers and other equipment protected.

  • Auxiliary contact provides better protection against electrical damages.

  • Auxiliary contact reduces the possibility of electrical failure.

  • Auxiliary contact contributes to circuit breaker durability.

Difference between the main contact and the auxiliary contact:



In an MCB, it is the principal contact mechanism that connects the load to the supply.Control, indicator, alarm, and feedback circuits use auxiliary contacts, also known as helpful contacts
The main contacts are NO (normally open) contacts, which signifies they will only establish contact when the MCB’s magnetic coil is powered.Both NO (Normally Open) and NC (Normally Closed) contacts are accessible in auxiliary contact
Main contact carries high voltage and high currentAuxiliary contact carries low voltage and low current
Sparking occurs due to high current
No sparking occurs in auxiliary contact
Main contacts are main terminal connection and motor connectionsAuxiliary contacts are utilised primarily in control circuits, indication circuits, and feedback circuits.

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