Buy Air Circuit Breaker (ACB) Online at Electrihub

An Air Circuit Breaker (ACB) is a high-capacity switching and protection device used to interrupt fault currents in low-voltage power distribution systems up to 1,000 V AC. Unlike moulded case circuit breakers (MCCBs), ACBs use ambient air as the arc-extinguishing medium and are specifically designed for incoming feeders, bus couplers, tie panels, and large outgoing feeder circuits in main distribution boards (MDBs), switchgear assemblies, and industrial power distribution centres (PDCs).

ACBs are rated and tested to IEC 60947-2, the international standard for low-voltage circuit breakers. Key parameters include the rated ultimate short-circuit breaking capacity (Icu), the rated service short-circuit breaking capacity (Ics), the rated uninterrupted current (Iu), and the rated operational current (In). Modern ACBs incorporate fully electronic trip units for overload (L), short-circuit (S and I), ground fault (G), and neutral protection — offering precise zone-selective interlocking (ZSI) and communication-ready interfaces for energy management systems.

ACBs are available in two primary configurations: fixed type (bolted directly into the switchboard) and withdrawable type (mounted on a chassis that slides into a cradle for maintenance without de-energising adjacent circuits). Withdrawable ACBs are the industry standard for critical infrastructure and industrial applications.

At Electrihub we stock Air Circuit Breakers from seven globally certified manufacturers — ABB, Schneider Electric, Siemens, Eaton, C&S Electric, HPL Electric, and Lauritz Knudsen (L&T) — covering frame sizes from 250 A to 6,300 A with breaking capacities up to 150 kA at 415 V AC.

Where Are Air Circuit Breakers Used?

Air Circuit Breakers are deployed wherever high fault currents must be reliably interrupted and sophisticated protection coordination is required. Common ACB applications include:

Main Incoming Feeders and Bus Sections — ACBs serve as the main incomer in Main LT Panels (MLTPs), Power Distribution Centres, and main switchboards in industrial plants, data centres, commercial buildings, and infrastructure projects. Their high breaking capacity ensures upstream fault isolation without damage to distribution transformers or cables.

Generator and UPS Paralleling Panels — ACBs with motorised closing, shunt trips, and under-voltage releases are used in automatic mains failure (AMF) panels to synchronise generators with the mains supply and provide controlled load transfer.

Industrial Power Distribution Centres (PDCs) and MCCs — Large manufacturing facilities, steel plants, cement factories, and process industries use ACBs for bus coupler duty and feeder protection where high fault levels and continuous high currents are present.

Data Centres and Critical Infrastructure — Tier III and Tier IV data centres rely on withdrawable ACBs for rapid, tool-free replacement during maintenance, combined with zone-selective interlocking to minimise outage zones during fault events.

Utility Substations and Power Receiving Stations — The secondary side of MV/LV distribution transformers is protected by ACBs rated for the transformer's prospective fault current, with built-in neutral protection and earth fault detection.

High-Rise Buildings and Commercial Complexes — Main incomer and bus-tie ACBs in basement substations and risers provide protection for large HVAC systems, lifts, escalators, and common-area electrical distribution.

Renewable Energy and Battery Energy Storage Systems (BESS) — ACBs with 4-pole configurations (switched neutral) are increasingly used in solar PV, wind, and BESS installations where reverse power flow, neutral management, and bidirectional current handling are required.

Air Circuit Breaker Brands and Series – Technical Comparison

The table below covers every ACB brand and series stocked by Electrihub. Use the current range, breaking capacity, and type columns to shortlist the right product, then follow the series link to browse available stock.

All ACBs are certified to IEC 60947-2. Icu values stated at 415 V AC, 50 Hz. Refer to individual product datasheets for derating curves, accessory compatibility, and full trip unit options.

About the ACB Brands We Stock

Schneider Electric — MasterPact MTZ and MasterPact NT ACB

Schneider Electric's MasterPact MTZ is the current-generation flagship ACB platform, covering 800 A to 6,300 A with an Icu of up to 150 kA at 415 V. The MTZ features the MicroLogic X electronic trip unit with an embedded energy meter, power quality analyser, and IO-Link / Modbus / PROFIBUS communication — eliminating the need for separate metering instruments on incoming feeders. The MasterPact NT series covers 630 A to 1,600 A and is widely specified for distribution boards and sub-incomer duties. Both series support zone-selective interlocking (ZSI), reducing fault damage and enabling selective tripping without time-delay compromise. Schneider ACBs are dual-listed to IEC and UL standards.

ABB — SACE Emax 2 and Formula Air ACB

ABB's SACE Emax 2 is the premium ACB range, rated 800 A to 6,300 A with breaking capacity up to 150 kA. The Emax 2 integrates ABB's Ekip trip unit family — available with Ethernet, Profibus, Modbus RTU, and IEC 61850 GOOSE messaging — making it the preferred choice for smart grid and digital substation applications. The ABB Formula Air (A1 to A6) is the current-generation standard ACB covering 250 A to 6,300 A, featuring a compact footprint, graphical display, and full arc flash calculation support. Both series support fixed and withdrawable configurations with spring-operated closing mechanisms for fast, reliable closure.

Siemens — SENTRON 3WL and 3WT ACB

The Siemens SENTRON 3WL is the top-of-range ACB platform with ratings from 630 A to 6,300 A and Icu up to 150 kA. The ETU (Electronic Trip Unit) 45B and 55B models offer integrated power measurement, load monitoring, and PROFINET / Modbus TCP communication, aligning with Siemens' TIA (Totally Integrated Automation) architecture. The SENTRON 3WT provides a cost-optimised solution from 630 A to 4,000 A for projects where advanced communication is not required. Both series support internal arc classification (IAC) and are available with arc flash mitigation accessories for enhanced personnel safety.

Eaton — IZM Series ACB

Eaton's IZM series (IZM91 and IZM101) covers 800 A to 6,300 A with Icu up to 150 kA. The IZM features a modular IZMX trip unit platform with optional power metering, harmonic analysis, and event logging. Eaton ACBs are compatible with the SmartWire-DT automation platform and support Modbus, PROFIBUS, and DeviceNet communication modules. The IZM series is particularly popular in process industries and data centres for its robust mechanical design and high IP rating options.

Lauritz Knudsen (L&T) — C-Power and U-Power ACB

Lauritz Knudsen's C-Power ACB is India's most widely specified domestic ACB platform, covering 800 A to 6,300 A with Icu up to 120 kA. Certified to IS/IEC 60947-2, C-Power is designed and manufactured in India, making it a preferred choice for government infrastructure projects, public sector undertakings (PSUs), and CPWD specifications. The U-Power series covers 630 A to 3,200 A for standard feeder and sub-incomer duties. Both series offer comprehensive trip unit options — from basic thermal-magnetic to fully digital units with MODBUS communication and load management functions. L&T ACBs are backed by one of the widest service networks in India.

C&S Electric — Cs-ACB Series

C&S Electric manufactures ACBs to IEC 60947-2 standards and is a trusted supplier for large government infrastructure, EPC contractors, and public utilities across India. The Cs-ACB series covers 800 A to 6,300 A with Icu up to 100 kA, and is available in both fixed and withdrawable versions with 3-pole and 4-pole configurations. C&S ACBs are offered with digital trip units supporting Modbus RTU communication, earth fault protection, and zone-selective interlocking for complex distribution systems.

HPL Electric — HAB Series ACB

HPL Electric's HAB series provides an IEC 60947-2 certified, cost-effective ACB solution for panel builders, OEMs, and commercial projects across South Asia. Covering 800 A to 4,000 A with Icu up to 85 kA, the HAB series offers fixed and withdrawable types in 3P and 4P configurations, with electronic trip units supporting overload, short-circuit, earth fault, and neutral protection functions.

How to Select the Right Air Circuit Breaker

Step 1 — Determine the rated current (In) and frame size

Calculate the maximum continuous load current on the feeder, including allowance for future load growth. Select an ACB whose rated operational current (In) equals or exceeds the maximum continuous load current. Apply a derating factor if ambient temperature exceeds 40°C or installation altitude exceeds 1,000 m above sea level.

Step 2 — Verify prospective short-circuit current (PSCC) and required Icu

Obtain the prospective fault current at the installation point from the transformer impedance or site power studies. Select an ACB with an Icu (ultimate breaking capacity) at least equal to the PSCC at that point. For critical incoming feeders, specify Ics = Icu (100% service breaking capacity) to ensure the ACB can remain in service after a fault event.

Step 3 — Choose fixed or withdrawable type

Select withdrawable ACBs for all critical incoming and bus-tie positions — they allow live maintenance, rapid replacement, and racking-out for isolation without tools or cable disconnection. Select fixed ACBs for outgoing feeders or budget-sensitive applications where downtime for maintenance is acceptable.

Step 4 — Select pole configuration (3P or 4P)

Choose 3-pole ACBs for three-phase TN-C (combined neutral and protective earth) earthing systems. Choose 4-pole ACBs where the neutral must be isolated and switched — required for TN-S and TT systems, generator changeover panels, and any installation with multiple sources of supply where neutral cross-connection must be prevented.

Step 5 — Specify the trip unit type and protection functions

For basic feeder protection, select a standard LSIG trip unit (Long-time / Short-time / Instantaneous / Ground fault). For energy metering, power quality monitoring, or integration with SCADA/BMS systems, select a communicating digital trip unit with Modbus RTU, PROFIBUS, or Ethernet interfaces. For installations requiring IEC 61850 interoperability, specify Siemens 3WL ETU, ABB Ekip COM, or Schneider MicroLogic X units.

Step 6 — Consider accessories and protection coordination

Specify accessories at the time of ordering: shunt trip coil (for remote opening), under-voltage release (UVR), motorised spring charging motor, closing coil, auxiliary and alarm contacts, and terminal shields. For systems with multiple ACBs in series, configure zone-selective interlocking (ZSI) to achieve selective tripping with minimum fault energy let-through.

Step 7 — Match brand to your switchboard ecosystem

For Type-tested switchgear assemblies (TTSAs) and Form 4 panels, select ACBs from the same manufacturer as the panel builder's type-tested board design to ensure form factor, cradle dimensions, and draw-out travel distances are correct. Cross-brand substitution in withdrawable ACBs requires re-testing of the panel assembly.

Key Technical Terms

Icu — Ultimate Short-Circuit Breaking Capacity

The maximum short-circuit current an ACB can interrupt once — after which the device may need to be inspected or replaced. Expressed in kA (rms symmetrical) at the rated operational voltage. This is the most important protection specification when sizing an ACB.

Ics — Service Short-Circuit Breaking Capacity

The short-circuit current the ACB can interrupt and remain fully serviceable for continued use — expressed as a percentage of Icu (typically 50%, 75%, or 100%). High-quality ACBs offer Ics = 100% Icu, meaning the breaker is fully operational after clearing a maximum fault.

Iu — Rated Uninterrupted Current

The maximum continuous current the ACB can carry without exceeding temperature limits, independent of its rated current setting (In). Iu is the thermal frame rating and is typically the maximum setting of the overcurrent trip unit.

LSIG Protection

The four fundamental protection functions of an electronic trip unit: L (Long-time overload), S (Short-time delay for selective coordination), I (Instantaneous overcurrent), and G (Ground fault / Earth fault). Advanced trip units add N (neutral protection) and additional functions such as arc flash detection and unbalance protection.

Zone-Selective Interlocking (ZSI)

A communication scheme between ACBs and MCCBs in a distribution hierarchy. When a downstream device detects a fault, it signals the upstream ACB to introduce an intentional trip delay — allowing the downstream device to clear the fault first. ZSI minimises the fault energy let-through and reduces arc flash hazard without sacrificing selectivity speed.

Withdrawable vs Fixed ACB

A withdrawable ACB is mounted on a chassis that can be racked out from the switchboard cradle to isolated, test, or removed positions without disconnecting main cables. A fixed ACB is bolted directly to the busbars. Withdrawable types are strongly preferred for critical incoming positions and bus-tie applications.

Motorised Operating Mechanism

An optional motor-charged spring closing mechanism that allows the ACB to be opened and closed remotely via a control signal — essential for AMF panels, remote switching schemes, and automation of distribution systems. Most ACBs can be fitted with manual or motorised spring charging at time of order.

Shunt Trip and Under-Voltage Release (UVR)

A shunt trip coil opens the ACB when energised by an external signal — used for fire alarm tripping, emergency stop, or remote open commands. An under-voltage release (UVR) opens the ACB when the supply voltage drops below a set threshold — preventing reconnection without deliberate operator action after a supply failure.

Frequently Asked Questions

What is the difference between an ACB and an MCCB?
An Air Circuit Breaker (ACB) is designed for high-current applications (typically 630 A to 6,300 A) with adjustable electronic trip units, withdrawable chassis, and communication interfaces. A Moulded Case Circuit Breaker (MCCB) covers lower currents (up to around 1,600 A), is generally fixed type, and is used for outgoing feeders and sub-distribution. ACBs offer far greater flexibility in protection settings, selectivity coordination, and metering than MCCBs.

What is the difference between Schneider MasterPact MTZ and MasterPact NT?
The MasterPact MTZ is the current-generation premium platform covering 800 A to 6,300 A with the MicroLogic X trip unit featuring embedded metering, Ethernet, and up to 150 kA Icu. The MasterPact NT covers 630 A to 1,600 A and is a more cost-effective option suited for distribution and sub-incomer duties. The NT uses the MicroLogic 2.0 to 7.0 trip unit range. Both share similar accessories and withdrawable cradle architecture.

Can I replace a Schneider MasterPact NT with a MasterPact MTZ?
Yes, in the overlapping current range (800 A to 1,600 A), the MTZ is designed to be a form-fit-function upgrade in the same withdrawable cradle as the NT. The MTZ's wider trip unit capabilities and MicroLogic X metering make it a future-ready replacement with no panel modification required in most cases.

What is the difference between ABB SACE Emax 2 and ABB Formula Air?
The SACE Emax 2 is ABB's flagship ACB with the highest breaking capacities (up to 150 kA), advanced Ekip trip units with IEC 61850 support, and premium arc flash mitigation features. The Formula Air (A-series) is ABB's standard ACB platform, offering a more cost-effective solution with Ekip touch and Ekip link trip units, suitable for the majority of industrial and commercial distribution applications.

What is the advantage of L&T C-Power ACB over imported brands?
Lauritz Knudsen (L&T) C-Power ACBs are manufactured in India to IS/IEC 60947-2, making them eligible for government and PSU projects requiring BIS certification and MAKE IN INDIA compliance. L&T's nationwide service network ensures fast spare-parts availability and on-site support across Tier 2 and Tier 3 cities where international brand service may be limited.

How do I calculate the ACB rating required for a 2,000 kVA, 415 V transformer?
The full-load current of a 2,000 kVA transformer at 415 V (three-phase) is approximately 2,782 A. With a 10% margin, the ACB should be rated at least 3,200 A In. You would also need to obtain the transformer impedance to calculate the prospective fault current and select the appropriate Icu — typically 65 kA to 100 kA for this transformer size.

What accessories are typically ordered with an ACB?
Standard accessories include: motorised spring charging motor (for remote/auto closing), shunt trip coil (for fire alarm or emergency open), under-voltage release (UVR), auxiliary contacts (for indication to SCADA/BMS), alarm contacts (trip indication), terminal end shields, and padlock accessories. For withdrawable types, position switches indicating connected/test/disconnected positions are also commonly specified.

Are all ACBs on Electrihub original and genuine?
Yes. Electrihub sources exclusively through authorised distribution channels for all brands including ABB, Schneider Electric, Siemens, Eaton, L&T, C&S, and HPL. All products are supplied in original manufacturer packaging with full traceability. Authenticity documentation and manufacturer certificates of conformity are available on request.

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