Auxiliary Contacts

An auxiliary contact is a low-current contact block that changes position together with the main contacts of a contactor, switch or miniature circuit breaker and reports to the control circuit whether the device is open or closed. It is used in control functions such as latching, electrical interlocking, driving pilot lights and carrying status information to a PLC input. For Schneider Electric TeSys and EasyPact, ABB, Siemens and Chint devices there are contact blocks in arrangements such as 1NO+1NC, 2NO, 2NO+2NC and 4NC, as well as signal contacts that report that the switch has tripped on a fault. Choose the auxiliary contact first by the brand and series of the device it will be fitted to, then by the number of NO and NC contacts, front or side mounting style, and the contact's rated current and voltage. In product names, normally open (NO) and normally closed (NC) contacts may also appear as NA and NK; because the blocks are series-specific, one may not fit another series. An auxiliary contact block must not be confused with an auxiliary contactor, which is a separate device operated by its own coil; the block carries only control current and is not used for load current.

Products

How to choose Auxiliary Contacts

An auxiliary contact is a low-current contact block that changes position together with the main contacts of a contactor, switch or miniature circuit breaker and reports to the control circuit whether the device is open or closed. It is used in control functions such as latching, electrical interlocking, driving pilot lights and carrying status information to a PLC input.

  • Separate overcurrent/leakage protection, motor starting and local isolation requirements.
  • Select rated current, pole count and breaking capacity (kA) from the installation calculation.
  • Match coil voltage, auxiliary contacts and tripping curve to the control circuit and load type.

Frequently asked questions

What is Auxiliary Contacts and where is it used?

An auxiliary contact is a low-current contact block that changes position together with the main contacts of a contactor, switch or miniature circuit breaker and reports to the control circuit whether the device is open or closed. It is used in control functions such as latching, electrical interlocking, driving pilot lights and carrying status information to a PLC input.

What should I compare when choosing Auxiliary Contacts?

Choose the auxiliary contact first by the brand and series of the device it will be fitted to, then by the number of NO and NC contacts, front or side mounting style, and the contact's rated current and voltage.

Where can I find technical details for Auxiliary Contacts products?

In product names, normally open (NO) and normally closed (NC) contacts may also appear as NA and NK; because the blocks are series-specific, one may not fit another series.

Switchgear Auxiliary and Trip Alarm Contacts Selection Guide