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Air Circuit Breaker(ACB) Connection Diagram and Wiring

Last Updated on: 2024-04-10T19:28:35Z , , ,


Hey, in this article, we are going to see the Air Circuit Breaker(ACB) Connection Diagram and its Wiring Procedure. Air Circuit Breakers (ACBs) are very important protective cum safety devices in electrical distribution systems. As they are used for medium to high-voltage electrical systems so their connection and wiring should be done to ensure the safety and efficiency of an electrical system. We can divide the Air Circuit Breaker Connection into two parts - the Power Circuit Connection and the Control Circuit Connection.

Power Supply Connection: In this part, ACBs are connected to the main power supply of the electrical distribution system. This connection is made through suitable cables or busbars, depending on the design of the system. It's important to ensure that the ACB is rated appropriately for the voltage and current of the system it is protecting. The output of the ACB is connected to the Load Centre through cables or busbars. The Power circuit of the ACB carries the actual high-voltage power that is to be switched or protected.

Control Circuit Wiring: ACBs come with control circuits that allow for manual operation, remote operation, and integration with other monitoring and control systems. These control circuit is used to control or proper functioning of the breaker. This includes connections for push buttons, indicating lamps, shunt trips, under-voltage releases, and other auxiliary devices.


Connection Diagram


Here, you can see the connection diagram of an Air Circuit Breaker.

ACB Wiring Diagram, Power and Control Circuit Connection of Air Circuit Breaker



Wiring Description


Power Circuit Connection

The incoming conductors from the power supply are to be connected to the designated incoming power terminals on the ACB. Depending on the design of the ACB, these terminals may be screw-type terminals, lug terminals, or busbar connections. Generally, three phases R, Y, and B are used for power circuit connection.

Similarly, the outgoing conductors from the ACB are to be connected to the load or distribution panel. Here also may be screw-type terminals, lug terminals, or busbar connections are used.

Control Circuit Connection

Remember that different types of Air Circuit Breakers from different manufacturers have different identifications and terminal names. Even they may need different types of connections. So, it is strictly advisable to consider the circuit diagram or connection instructions provided by the manufacturer. Here, we have explained a generic connection procedure that will help you to understand how actually an ACB is wired.

As you can see in the above connection diagram, a double pole MCB is used as the control MCB that switches and protects the control circuit.
  • The terminals of the ACB - 95, U1, D1, 11, and 21 are connected to the phase supply from the output of the Control MCB.
  • The terminals of the ACB - U2, D2, C2, and C12 are connected to the neutral supply from the output of the Control MCB.
  • The input of both push button switches is connected to the phase supply from the output of the Control MCB.
  • The output of the START push button switch(NO) is connected to the C1 terminal of the ACB.
  • The output of the STOPT push button switch(NC) is connected to the C11 terminal of the ACB.
  • The negative terminals of all the indication lamps are connected to the neutral supply from the output of the Control MCB.
  • The phase terminal of the ON indication lamp(Green) is connected to terminal 12(NO) of the ACB.
  • The phase terminal of the OFF indication lamp(RED) is connected to terminal 22(NC) of the ACB.
  • The phase terminal of the TRIP indication lamp(Yellow) is connected to terminal 96(NO) of the ACB.

Here, 95 and 96 terminals are used for the tripping operation of the ACB. As these terminals are connected to the trip indication lamp, so when the ACB gets tripped the trip indication lamp will glow.

U1 and U2 terminals are utilized for supplying power to the charging motor inside the ACB.

D1 and D2 terminals are used for undervoltage protection. They provide the signal to the under-voltage coil of the ACB. When the Undervoltage protection system receives signals indicating when the voltage falls below a certain predefined threshold, triggering the ACB to trip and disconnect the power supply to prevent damage to the equipment.

C1 and C2 terminals are used to turn on the ACB from an external or remote location. They are connected to a NO push button switch. So when the push button switch is pressed the ACB will turn On.

Similar to C1 and C2, these C11 and C12 terminals are used to turn off the ACB from an external or remote location. They are connected to the NC push button switch. So when the push button switch is pressed the ACB will turn Off.

11 and 12 terminals provide a normally open (NO) contact that closes when the ACB is in the ON position. These terminals are used to indicate whether the ACB is in the closed or ON position. They are often connected to indicator lamps(here connected to Green Lamp) or control systems to provide visual or remote indication of the breaker's status.

21 and 22 terminals provide a normally closed (NC) contact that opens when the ACB is in the OFF position. Similar to terminals 11 and 12, these terminals indicate whether the ACB is in the open or OFF position. They are also connected to indicator lamps(here connected to Red lamps) or control systems to provide status indication.



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Air Circuit Breaker(ACB) Connection Diagram and Wiring Air Circuit Breaker(ACB) Connection Diagram and Wiring Reviewed by Author on April 10, 2024 Rating: 5
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