What it is and what it does
The Siemens 3VA2440-6HM42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 400 A continuous current across the full ambient range from -25 °C to 70 °C — no derating needed up to that ceiling. Its 4-pole design with an ETU330 electronic trip unit makes it a line-protection breaker for main feeders or large sub-distribution in industrial panels. The interrupting ratings are the headline: 242 kA at 240 V, 187 kA at 415 V and 440 V, 121 kA at 500 V, and 9 kA at 690 V — so it handles high-fault scenarios at common low-voltage levels without cascading upstream gear.
What the ratings mean for fit
The 400 A continuous rating holds flat from 40 °C through 70 °C — that's unusual; most breakers derate above 40 °C. If your panel ambient runs hot (say, 55 °C near a transformer), this breaker still delivers full 400 A without oversizing. The ETU330 electronic trip offers adjustable N-conductor protection (OFF, 50%, or 100% of phase rating), which matters for 4-wire systems where the neutral may carry harmonic currents. Ground-fault monitoring uses summation current on L+N — no external CT needed.
Where it goes in the panel
Mounts on a DIN rail or direct panel-mount via the 248 mm height, 184 mm width, 110 mm depth footprint. The IP40 front protection means it's fine inside a closed enclosure but not for washdown zones. Max power loss is 63.5 W — plan ventilation if you're stacking multiple breakers in a sealed cabinet.