Industries use 6 types of ACB: pole type, current capacity type, fix or drawout type, breaking capacity type, operation type, and protection type.
6 Major Types of ACB (Air Circuit Breaker)
Different types of Air Circuit Breakers (ACBs) are available for various applications, such as pole, current capacity, installation type, and breaking capacity. Details of the different types of ACBs are given below.
- According to pole type
- Current Capacity type
- Mounting- Fixed or draw out type
- According to Breaking Capacity
- EDO and MDO type ACB
- Protection type ACB
1. Pole Type ACB
A pole of a circuit breaker refers to the part of the breaker that is associated with one conducting path in the main circuit.
Three-Pole ACB –The circuit breaker with a 3-pole has three separate conducting paths. It is used for 3-phase, 3-wire electrical system.
Four-Pole ACB –The 4-pole ACB has four separate conducting paths. It is used for 3-phase, 4-wire electrical system. A 4-pole ACB allows isolation of the neutral conductor
2. Types of ACB: According to the Current Capacity
The current rating capacity of ACBs ranges from 400A to 6300A. Below are the details:
| S.N | Current Rating |
| 1. | 400A |
| 2. | 600A |
| 3. | 800A |
| 4. | 1000A |
| 5. | 1200A |
| 6. | 1600A |
| 7. | 2000A |
| 8. | 3200A |
| 9. | 4000A |
| 10. | 5000A |
| 11. | 6300A |
3. Fixed or Draw Out Types ACB
Fixed Type- Fixed type ACB is mounted on the panel’s chassis and cannot be drawn out. The draw-out mechanism, such as the cradle and safety shutter, are not used. It is a low-cost ACB compared to a draw-out ACB.
Draw-out type – Draw-out air circuit breakers (ACBs) are widely used in industries. They can be easily moved on a cradle for maintenance purposes, both inside and outside. The best part is that they can be replaced without changing the base chamber, meaning that faulty ACBs can be replaced with new ones quickly and easily.
4. Types of ACB: According to Breaking Capacity
As per the breaking code, the breaking capacity of ACB ranges from 25KA to 200KA. The details are given below.
| Sr.No. | Breaking Code | Breaking value |
|---|---|---|
| 1 | B | 25KA/440 Volt |
| 2 | F | 36KA/440 Volt |
| 3 | N | 50KA/440 Volt |
| 4 | H | 70KA/440 Volt |
| 5 | S | 100KA/440 Volt |
| 6 | L | 150KA/440 Volt |
| 7 | R | 200KA/440 Volt |
| 8 | HB1 | 75KA/690 Volt |
| 9 | HB2 | 100KA/690 Volt |
| 10 | K | 10KA/1000 Volt |
In addition to these breaking capacity codes, Air Circuit Breakers are also classified based on their arc quenching techniques. These are essential in defining how the arc formed during breaking is extinguished, ensuring safe interruption. Below are the common types:
Plain Break Type ACB
This is the simplest form of ACB where the arc is extinguished in open air without any assistance from magnetic or mechanical devices. It is suitable for low-capacity applications, but its performance is limited in high short-circuit conditions due to poor arc control.
Magnetic Blow-Out Type ACB
In this type, magnetic fields are used to stretch and move the arc into arc chutes, thereby increasing the arc length and aiding in quicker extinguishing. This type is more effective than plain break ACBs, especially in moderate short-circuit duties.
Air Chute ACB
This is the most commonly used type in industrial applications. The arc is driven into arc chutes where it is divided into multiple smaller arcs using splitter plates, reducing arc energy and allowing faster quenching. Air chute ACBs can handle higher breaking capacities and are preferred for modern power systems.
For more details, see Arc Quenching Techniques in Air Circuit Breakers.
5. According to Operation as EDO & MDO Type
ACB has two types of operations: EDO (electrically draw out) and MDO (mechanically draw out).
EDO Operation: The EDO-type ACB can be easily operated remotely from any distance through a networking system. It mainly has three functions, which are listed below:
- Spring Charging: In auto mode, an electrical motor charges the spring.
- Closing Coil: The system can be operated either via a TNC or remotely through a PLC or BMS system.
- Shunt Coil or tripping Coil: The shunt or tripping coil can be operated using TNC or remotely through PLC or BMS.
When the ACB is charged and closed using the electrical release, it is called the EDO type. Spring charge motors are used for spring charging, and a closing coil is used for closing the breaker.
Mechanically operated draw out (MDO)-The MDO type ACB can only be operated manually and cannot be operated through any other source. When the ACB is charged manually without the spring charge motor and closed without the closing coil, it is called an MDO-type ACB. Two press buttons are used to start and stop the ACB. To switch it on, we need to press the ‘on’ button and to stop it; we have to press the ‘stop’ button.
Difference Between MDO and EDO ACB
| Feature | MDO (Mechanically Draw Out) | EDO (Electrically Draw Out) |
|---|---|---|
| Mode of Operation | Manual operation only | Electrical (remote/automatic) operation |
| Spring Charging | Manual | Via motor |
| Closing Mechanism | Manual (push button) | Through closing coil |
| Remote Operation | Not possible | Possible (via PLC/BMS/TNC) |
| Usage | Basic applications | Advanced systems with automation |
| Cost | Lower | Higher due to motorized features |
6. According to Protection Type ACB
Thermal-magnetic trip- Thermal-magnetic trip units are effective in safeguarding against overcurrent and short circuits using traditional methods.
Electronic Trip: Intelligent operation and reflex tripping are combined in electronic trip units, which are faster and more accurate.
Modern ACB relay types used in electronic trip units are configurable based on the protection level required in industrial power systems. The most common relay types include:
- LSI – Provides Long Time, Short Time, and Instantaneous protection.
- LSIG – Offers Long Time, Short Time, Instantaneous, and Ground Fault protection.
- LI – Covers Long Time and Instantaneous protection.
- LS – Includes Long Time and Short Time settings.
These relay settings help ensure the ACB responds accurately and selectively to various fault conditions in industrial power systems.
Conclusion
Choosing the right type of ACB depends on application needs—be it basic thermal protection or advanced remote operation. Whether you need fixed or draw-out, EDO or MDO, or protection via LSI/LSIG settings, understanding these types helps ensure system safety, easy maintenance, and power continuity.
Frequently Asked Questions (FAQs)
ACBs can be categorized based on pole count, current capacity, installation method (fixed/draw-out), breaking capacity, operation type (EDO/MDO), and protection method.
A 3-pole ACB controls three conductors and is used in 3-phase, 3-wire systems. A 4-pole ACB includes a neutral pole, making it suitable for 3-phase, 4-wire systems where neutral isolation is needed.
EDO stands for Electrically Draw-Out, and MDO stands for Mechanically Draw-Out. These refer to how the ACB operates and is maintained.
Draw-out ACBs offer easier maintenance and replacement, making them ideal for industrial applications. Fixed ACBs are cost-effective but not service-friendly.
Electronic trip units offer customizable protection like LSI (Long, Short, Instantaneous) and LSIG (including Ground Fault), making them ideal for modern automation systems.
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