ACBs are critical low-voltage protection devices used to safeguard electrical systems from overcurrent and short-circuit conditions. Let’s understand the ACB full form in electrical, how it works, and where it’s used.
What is ACB & Its Full Form?
The full form of ACB in electrical is Air Circuit Breaker. An air circuit breaker is a device used in low-voltage electrical systems, typically 415 volts, to control power flow and provide overcurrent and short circuit protection.
Air circuit breakers use relays and releases to protect loads from different kinds of faults. When a fault occurs, these devices trip the circuit breaker to prevent damage. Releases are sensing devices that are installed inside the breaker, while relays are installed outside of it. Releases are internal features of ACB, while relays are external.
Now that we understand the ACB full form in electrical and its basic application, let’s explore how it works in detail.
How ACBs Work (Working Principle)
The working principle of an ACB (Air Circuit Breaker) is similar to circuit breakers such as SF6 circuit breakers and vacuum circuit breakers, which are used in HT supply. In HT circuit breakers, an extra arc quenching medium such as oil, SF6, or vacuum is required due to the high voltage.
On the other hand, in Low Voltage (LV) systems, no additional quenching medium is necessary as the arc is extinguished in normal ambient air. However, special internal arrangements—such as arcing horns and arc chutes—are incorporated within the breaker to assist in effective arc extinction.
As a key component in overcurrent protection in LV systems, an ACB ensures safe power interruption during electrical faults.
Arc Interruption Methods in ACB
Arcing horns
Arcing horns increase the contact area and spread arc heat between fixed and moving contacts.
Arc Chutes
Arc chutes are installed above the contacts. These chutes split the heat generated by the electric arc inside the chamber, which causes the arc to cool down, lengthen, and split. This results in the voltage of the arc becoming much higher than the voltage of the system when the ACB is closed. Eventually, the arc is quenched automatically.
Important ACB Terms and Components
The following are key Air Circuit Breaker components and operational terms essential for understanding how ACBs function in low-voltage protection systems.
Fixed Type ACB – This breaker is fixed with the cradle, and the cradle is attached to the panel, making it impossible to remove the breaker.
MDO ACB – MDO stands for Manually Operated Draw Out type of breaker. The breaker is operated manually, and it can be racked in and out with the help of a handle.
EDO ACB – EDO stands for Electrically Operated Draw Out type of breaker. This breaker can be operated both electrically and manually; it can be easily racked in and out with the help of a handle.
👉 For a complete explanation of all configurations and construction-based variations, refer to our detailed guide on the Types of ACB (Air Circuit Breakers).
Releases – These relays are fitted inside the breaker for various types of protection. There are different types of releases:
- Shunt Release – This release is used to trip a breaker remotely. When the shunt release is energized, it sends a command to trip the breaker, and the breaker mechanism disconnects the contacts.
- Undervoltage Release – It trips when the voltage drops below 80% of the supply voltage to protect equipment from low voltage. You can set the undervoltage release setting as per the system requirement.
- Electromagnetic or Electronic Release – There are two types of ACBs available in the market based on their release mechanism: electromagnetic and electronic. In electromagnetic releases, trip settings are fixed in percentage steps for fault protection. However, electronic releases allow for customizable trip settings. Additionally, electronic releases have a faster response time compared to electromagnetic releases.
Poles – Circuit breakers come in different configurations, such as 4P, TP, and TPN. Here are the details:
- 4P ACB – When an ACB operates, all three phases (R, Y, B) and one neutral will operate in the 4P configuration.
- TP ACB – It is a 3-pole ACB. When the TP breaker is activated, only the R, Y, and B phases are involved in the breaker’s operation. The neutral is connected through a link and is not part of the ACB.
- TPN ACB – TPN stands for Triple Pole with Neutral. In this configuration, the R, Y, and B phases and the neutral are part of an ACB (Air Circuit Breaker). When the ACB operates, only the R, Y, and B phases operate, and the neutral does not. However, the neutral remains connected.
Understanding these important terms helps in applying the ACB full form in electrical—Air Circuit Breaker—effectively in real-world electrical systems.
Applications of ACB in Electrical Systems
Air Circuit Breakers are widely used in various low-voltage applications where high reliability and safety are required. Some of the key applications include:
- Industrial Electrical Panels: ACBs serve as low-voltage protection devices, protecting motors, transformers, and generators from overload and short-circuit conditions.
- Power Distribution Systems: Used in main distribution boards for commercial buildings, hospitals, and malls.
- Renewable Energy Systems: Suitable for controlling and protecting solar or wind power inverters.
- Data Centers and IT Facilities: Ensures uninterrupted power with fast fault detection and isolation.
ACB vs MCCB – Key Differences
| Feature | ACB (Air Circuit Breaker) | MCCB (Moulded Case Circuit Breaker) |
|---|---|---|
| Voltage Range | Up to 690V (mostly LT systems) | Up to 690V (LT systems) |
| Current Rating | Up to 6300A | Up to 1600A |
| Breaking Capacity | High | Moderate |
| Applications | Industrial panels, power stations | Small industries, commercial buildings |
| Price | More expensive | Economical |
| Features | Advanced (electronic trip units, remote trip) | Basic protection |
Frequently Asked Questions (FAQs)
Below are some commonly asked questions about ACBs for quick reference.
ACB stands for Air Circuit Breaker. It is a switching and protection device used in low-voltage electrical systems to interrupt fault currents such as overloads and short circuits.
ACBs are designed for higher current ratings (up to 6300A) and come with advanced features like remote tripping and electronic releases, making them suitable for industrial applications. MCCBs are compact and economical, typically used in smaller commercial setups with lower current ratings (up to 1600A).
ACBs are commonly used in industrial electrical panels, power distribution systems, commercial buildings, and data centers, where reliable protection and high breaking capacity are required.
No, ACBs are not used in home wiring due to their large size and high capacity. For homes, MCBs (Miniature Circuit Breakers) are more appropriate.
The main function of an ACB (Air Circuit Breaker) is to protect electrical circuits and equipment from damage due to overloads, short circuits, or other electrical faults by automatically breaking the circuit when a fault is detected.
The full form of ACB panel is Air Circuit Breaker panel. It is an integrated panel setup that includes the ACB unit along with supporting components like relays, busbars, and wiring, used for controlling and protecting power distribution in industrial systems.
Conclusion
ACBs or Air Circuit Breakers are essential components in low-voltage electrical protection systems. Understanding the ACB full form in electrical, its operation, types, and applications helps ensure safe and efficient power distribution in industrial and commercial environments.
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