Types of Relays Used in Air Circuit Breaker (ACB)

Basically internal protection and tripping applications, relays are used internally in air circuit breakers to make it more efficient in operation. And generally three types of relays are used in air circuit breaker.

• shunt coil relay
• Under Voltage (UV) Relay
• closing relay

Shunt Coil Relay

Basically this relay can also be called as power relay for air circuit breaker. Shunt coil relay is an automatically controlled relay, which can be operated remotely to open or close a circuit breaker.

Just like a PLC operates a relay, this shunt coil relay can also be operated (on or off) by it. The operation of this relay directly opens or closes the circuit breaker.

Under Voltage (UV) Relay

Basically this relay is used to detect under voltage in the incoming power supply. Overvoltage is a simple natural problem that the circuit breaker will detect and trip the path. When the incoming voltage is low and usually less than 380 V, the load connected in the circuit breaker will work in low efficiency and also get damaged after a long time. So, an under-voltage relay is used to detect under-voltage problems and trip the circuit for it immediately. You can set an under-voltage threshold in the circuit breaker, which will then automatically perform this protection function.

Closing Relay

Basically it is same as shunt coil relay. It can also be controlled remotely via PLC, and it will automatically open or close the circuit breaker.