Air Circuit Breaker [ACB]

An air circuit breaker (ACB) is the main protection device of a low-voltage switchboard. It is used as the incomer of an LT panel and for very large outgoing feeders, and opens automatically on overload, short circuit and earth fault.

ACBs have electronic trip units with adjustable settings, high breaking capacity and, in draw-out versions, can be racked out safely for maintenance.

Available ratings

800A – 6300A

Where it is used

• Main incomer of LT panels and MDBs fed from a transformer
• Generator incomers and bus couplers
• Very large outgoing feeders, such as chillers or busbar risers
• Automatic transfer (ATS) panels with motorised ACBs

How to choose

• Rated current: match the transformer or generator full-load current (about 1.39 A per kVA at 415 V).
• Breaking capacity: higher than the fault level at the panel.
• Fixed or draw-out: draw-out makes maintenance safer and faster.
• Trip unit: basic LSI protection, or metering and communication for building management systems.
• Poles and accessories: 3 or 4 poles, motor operator, shunt trip, undervoltage release and auxiliary contacts.

Why buy from Unique Quality Engineering

Since 2012 we have supplied genuine components from ABB, Schneider Electric, Siemens, Mitsubishi and Fuji Electric to panel builders, factories and contractors across Bangladesh. Our engineers help you choose the right rating and model, and we use the same parts in the panels we build ourselves.

Frequently asked questions

What is the difference between an ACB and an MCCB?

An ACB is used for large currents, typically from about 630–800 A up to 6300 A, and has fully adjustable electronic protection and draw-out options. An MCCB covers smaller ratings, usually up to 1600 A. See our ACB vs MCCB vs MCB guide.

Which ACB rating do I need for a 1000 kVA transformer?

A 1000 kVA transformer at 415 V has a full-load current of about 1391 A, so a 1600 A ACB is the usual choice. Our engineers confirm the rating from your single-line diagram.

Do you supply ACB spare parts and accessories?

Yes. We supply trip units, motor operators, shunt trips, undervoltage releases and other accessories for common ACB ranges.

Need a price for an ACB? Request a quotation with the rating and quantity, or call or WhatsApp +8801992-389515.