Siemens 3VT8440‑2AA04‑2GA2 – 4‑Pole Molded Case Circuit Breaker

The Siemens 3VT8440-2AA04-2GA2 is a 4‑pole molded case circuit breaker (MCCB) from the 3VT series, designed for reliable overload and short‑circuit protection in low‑voltage power distribution systems. This breaker offers a rated current of 400 A and a breaking capacity of 50 kA at 415 V AC, making it suitable for main switchboards, sub‑distribution panels, and motor control centers.

Protection Mechanism

The breaker employs a thermal‑magnetic trip unit. The thermal element provides inverse‑time overload protection, while the magnetic element delivers instantaneous tripping for short‑circuit faults. The trip unit is fixed with preset thresholds, ensuring consistent performance. The 4‑pole design allows switching of all three phases plus neutral, with the neutral pole typically delayed to ensure pole‑to‑pole coordination.

Breaking Capacity and Electrical Ratings

With a rated ultimate breaking capacity (Icu) of 50 kA at 415 V AC, this MCCB can handle severe fault currents without damage. The rated service breaking capacity (Ics) is 100% of Icu, enabling repeated interruption of fault currents. The insulation voltage is 800 V AC, and the impulse withstand voltage is 8 kV. The breaker is suitable for use in systems with a frequency of 50/60 Hz.

Mechanical Construction

The housing is made of high‑strength thermoset plastic, providing excellent arc resistance and mechanical robustness. The 4‑pole unit is compact, with dimensions suitable for standard panel mounting. The breaker features front‑mounted terminals for cable or busbar connections, with clear labeling for line and load sides. The operating handle is central and can be locked in the OFF position for safety during maintenance.

Accessories and Auxiliaries

A range of accessories is available, including shunt trips, undervoltage releases, auxiliary contacts, and alarm switches. These allow remote tripping and status indication, integrating the breaker into automation systems. The 3VT series also supports plug‑in and draw‑out versions for easy replacement without disconnecting cables.

Environmental and Compliance

The breaker operates in ambient temperatures from -5 °C to +55 °C, with derating for higher temperatures. It is rated for pollution degree 3 and has an IP20 protection degree for the enclosure. The product carries CE, UL, and CCC certifications, complying with IEC 60947‑2 and UL 489 standards. It is also RoHS compliant.

Applications

Typical applications include main incoming protection, feeder circuits, motor branch circuits, and welding machine supplies. Its high breaking capacity makes it ideal for industrial plants, commercial buildings, and data centers requiring reliable power distribution.

Installation and Wiring

Mounting is by screw fixing to a mounting plate, with specified torque values for terminal connections. The breaker is suitable for both copper and aluminum conductors. A comprehensive instruction manual provides guidance on cable sizing, clearance distances, and coordination with upstream/downstream devices.

Maintenance and Lifecycle

Routine inspection of terminal tightness and operation of the mechanism is recommended. The breaker is maintenance‑free for most applications, but periodic testing of the trip function is advised for critical installations. Spare parts and replacement units are available through Siemens’ service network.

Overall, the Siemens 3VT8440‑2AA04‑2GA2 delivers robust, reliable circuit protection, ensuring the safety and continuity of power distribution in demanding environments.