| Fixed-Frame ACB | Bolted directly into a low-voltage switchboard or panel. | Approximately 630–6,300 A, depending on the frame design and manufacturer. | Commonly up to 690 V AC in industrial and commercial systems. | When a fault is detected, the trip unit releases the operating mechanism. The contacts separate in air, while arc runners and arc chutes divide, cool, and extinguish the arc. | Long-time overload, short-time short circuit, instantaneous short circuit, and optional earth-fault protection. | Main incoming feeders, bus couplers, large industrial distribution boards, and generator connections. |
| Draw-Out ACB | Mounted on a cradle with connected, test, and disconnected positions. | Approximately 630–6,300 A, subject to frame size and rated current. | Commonly up to 690 V AC; higher system ratings require specific equipment verification. | The breaker can be electrically isolated without removing it from the switchboard. Primary and secondary disconnects allow testing and maintenance in the withdrawn position. | Adjustable long-time, short-time, instantaneous, and earth-fault protection; optional zone-selective interlocking. | Critical facilities, data centers, hospitals, utilities, and systems requiring rapid maintenance or replacement. |
| Manual-Operating ACB | Fixed or draw-out installation with local mechanical control. | Approximately 630–6,300 A. | Typically up to 690 V AC. | A spring or stored-energy mechanism is charged and released manually. The contacts close or open through the mechanism, while the trip unit opens the breaker automatically during a detected fault. | Usually includes overload and short-circuit protection; earth-fault and other functions depend on the trip unit. | Standard distribution systems where local operation is sufficient and remote switching is not required. |
| Electrically Operated ACB | Fixed or draw-out installation with motor charging and shunt or undervoltage releases. | Approximately 630–6,300 A. | Typically up to 690 V AC. | An electric motor charges the closing spring. A closing release closes the contacts, while a shunt-trip release or undervoltage release opens the breaker when commanded or when control voltage conditions require it. | Overload, short circuit, earth fault, remote trip, undervoltage release, and optional under/overvoltage functions. | Automatic transfer systems, generator synchronization, energy-management systems, and remotely controlled substations. |
| Thermal-Magnetic Air-Break Device | Usually used in compact low-voltage air-break molded-case designs rather than large power ACBs. | Commonly from a few amperes to approximately 1,600 A, depending on the frame and construction. | Commonly up to 600–690 V AC, depending on the applicable standard and product design. | A bimetal element responds to sustained overload heating, while a magnetic element responds rapidly to high short-circuit current. Both mechanisms open the contacts in air. | Thermal overload and magnetic short-circuit protection; earth-fault protection is not inherent unless separately provided. | Feeder circuits, motor branches, lighting distribution, and general low-voltage panel protection. |
| Electronic-Trip ACB | Fixed or draw-out switchgear, generally for high-current distribution. | Approximately 630–6,300 A, with adjustable settings based on the selected frame and sensor rating. | Commonly up to 690 V AC. | Current sensors measure phase current and send signals to an electronic trip unit. The trip unit compares the measured values with programmed thresholds and activates the opening mechanism when required. | Long-time, short-time, instantaneous, and earth-fault protection; metering, alarms, communications, and event recording may be available. | Power distribution with coordination, selectivity, energy monitoring, and advanced maintenance requirements. |
| Current-Limiting Air-Break Design | Specialized low-voltage equipment installed where prospective fault current is high. | Varies widely; selection depends on the rated current and tested interrupting performance. | Commonly low-voltage AC systems up to approximately 690 V. | Contact geometry and arc-control components increase the speed of current interruption and limit the peak let-through current and associated thermal and mechanical stress. | Short-circuit interruption with conventional overload and optional earth-fault functions. | High-fault-level switchboards, industrial plants, transformer secondaries, and installations requiring reduced fault energy. |
| Air Circuit Breaker with Zone-Selective Interlocking | Coordinated switchboards with multiple protection levels. | Typically 630–6,300 A. | Commonly up to 690 V AC. | Trip units exchange restraint or coordination signals. The breaker nearest the fault can trip with a short intentional delay, while upstream breakers remain closed when their protection is not required. | Long-time, short-time, instantaneous, earth-fault, and zone-selective interlocking functions. | Large commercial buildings, manufacturing plants, infrastructure, and systems requiring improved selectivity. |
| Generator-Protection ACB | Generator output switchboards and synchronizing panels. | Selected to match generator full-load current; commonly hundreds to several thousand amperes. | Typically 400–690 V AC for low-voltage generator systems. | The breaker connects or disconnects the generator from the bus. Its trip unit and control circuits coordinate with generator protection, synchronization, reverse-power, and automatic-transfer functions. | Overload, short circuit, earth fault, undervoltage, reverse power, and other functions through dedicated protection and control systems. | Standby generators, prime-power systems, microgrids, and parallel-generation installations. |
