An Air Circuit Breaker (ACB) is a low-voltage protection device that safeguards electrical systems from overload, short-circuit, and earth faults. Operating in air as the arc extinguishing medium, ACBs are widely used in LV panels, transformers, and industrial power distribution up to 690 V and 6,300 A.
Description
An Air Circuit Breaker (ACB) is a type of circuit breaker that operates in the air (at atmospheric pressure) as the arc extinguishing medium. It is used for low-voltage (LV) applications, typically up to 690 V AC and 6,300 A. ACBs provide overload, short-circuit, and earth fault protection and can also be used as a main incoming circuit breaker in LV panels.
Specifications
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Voltage Rating: Up to 690 V AC (low voltage applications)
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Current Rating: 630 A to 6,300 A
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Breaking Capacity: 50 kA to 100 kA (depending on model)
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Poles: 3-pole / 4-pole
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Operating Mechanism: Manual (spring-charged) / Motorized
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Standards: IEC 60947-2
Features
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Arc Quenching in Air: No special medium required, easy maintenance
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Multiple Protections: Overload, short-circuit, earth fault, under-voltage
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Flexible Installation: Fixed type or draw-out type
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Advanced Versions: Microprocessor-based trip units with communication (Modbus, Ethernet)
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High Breaking Capacity: Ensures reliable protection in LV distribution
Applications
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Main incoming breaker in LV switchgear panels
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Power distribution in industrial plants, commercial complexes, and data centers
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Backup protection for transformers, generators, and large motors
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Used in utility substations for LV systems
Advantages
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Simple design and reliable operation
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High breaking and making capacity
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Easy to install and maintain
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Can be motorized for remote operation
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Available with advanced electronic trip units
Disadvantages
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Bulky size compared to MCCB or MCCB alternatives
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Limited to low-voltage applications (not suitable for >1 kV)
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Higher cost compared to MCCBs in smaller ratings
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Requires regular inspection due to air as arc medium
