What this 400 A MCCB really delivers
The Siemens 3VA2340-0KQ42-0AA0 is a SENTRON 3VA2 molded case circuit breaker rated for 400 A continuous current, with an ETU860 electronic trip unit that adjusts from 600 A minimum to 4800 A maximum — that's a wide 8:1 range for coordinating with transformer inrush or motor starting curves without swapping the breaker frame. Breaking capacity hits 440 kA at 415 V and still holds 187 kA at 690 V, which puts this squarely into high-fault industrial switchgear — think large motor control centers, transformer secondaries, or main feeders where the available fault current is serious enough to vaporize a standard 65 kA breaker. The 4-pole configuration with summation ground-fault monitoring (L + N conductor) means it can serve as a main breaker in a TN or TT system where the neutral needs both protection and ground-fault detection, not just a switched neutral bar. Communication function is built in — the ETU860 supports the SENTRON communication platform for power monitoring and remote trip indication, so this breaker can report its status back to a BMS or SCADA without an add-on module.
Thermal limits — where the rating holds and where it drops
At 55 °C it derates to 375 A, at 60 °C to 350 A, at 65 °C to 325 A, and at 70 °C to 300 A. In a multi-breaker lineup, that heat adds up and drives ventilation sizing.
Panel fit and physical integration
Dimensions are 248 mm high, 184 mm wide, 110 mm deep — a 4-pole frame that fits standard Siemens 3VA2 mounting patterns. The IP40 front protection means it's suitable for enclosed switchgear where the door provides the full IP rating; it's not a standalone outdoor breaker without an enclosure. The N-conductor protection is adjustable from OFF to 20%–100% of the phase current, which lets you match the neutral protection to the harmonic load profile — critical for data center or VFD-heavy panels where triplen harmonics overload the neutral.