Specifying the right circuit breaker starts with understanding which category it belongs to. ACBs, VCBs, and MCCBs are all built for different voltage classes and applications — mixing them up leads to either an oversized, overpriced installation or, worse, an underprotected one.
Air Circuit Breaker (ACB)
ACBs interrupt current in open air (sometimes with arc chutes to help quench the arc) and are used almost exclusively on low-voltage (LV) systems, typically at the main incoming supply of a building or plant, rated from around 630A up to 6300A. They're the standard choice for a facility's main LV switchboard where high current-carrying capacity and adjustable protection settings (via an electronic trip unit) are needed.
Vacuum Circuit Breaker (VCB)
VCBs are built for medium-voltage (MV) systems, typically 3.3kV to 36kV, and use a sealed vacuum interrupter to break current. They're the standard for utility substations, MV switchgear feeding large motors and transformers, and industrial captive power distribution. See our full VCB guide for details.
Moulded Case Circuit Breaker (MCCB)
MCCBs sit at the lower end of the LV current range compared to ACBs — typically 100A to 2500A — and are housed in a compact moulded insulating case. They're used for sub-distribution boards, feeder protection, and motor protection within a facility, downstream of the main ACB. See our MCB vs MCCB comparison for how they differ from the smaller MCB.
Comparison Table
| Parameter | ACB | VCB | MCCB |
|---|---|---|---|
| Voltage Class | LV (up to 1000V) | MV (3.3kV–36kV) | LV (up to 1000V) |
| Current Rating | 630A–6300A | 630A–4000A (MV side) | 100A–2500A |
| Interrupting Medium | Air | Vacuum | Air (moulded case) |
| Typical Use | Main LV incomer | MV switchgear, substations | Sub-distribution, feeders, motors |
Making the Right Choice
Start with your system voltage — that alone rules out either ACB/MCCB (both LV) or VCB (MV). Within LV, choose ACB for the main incoming supply where high current and adjustable protection are needed, and MCCB for downstream feeders and sub-boards. If in doubt, share your single-line diagram and fault level study with our team.
Request a quote and we'll help you specify the right breaker type and rating for each point in your distribution system.