What this MCCB carries — and what it means for your panel
The Siemens SENTRON 3VA2340-5HN32-0AH0 is a 3-pole molded case circuit breaker rated for a continuous current Iu of 400 A, with an ETU350 electronic trip unit onboard. That 400 A holds flat from 40 °C up through 50 °C, then derates to 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, and 340 A at 70 °C — so if your panel runs hot near a row of drives, you still have headroom without upsizing the frame. The interrupting ratings climb to 187 kA at 240 V, drop to 121 kA at both 415 V and 440 V, then 75.6 kA at 500 V, and 17 kA at 690 V. For a 400 A line-up on a 480 V secondary, that 75.6 kA gives you real selectivity headroom against a downstream feeder fault — you're not chasing coordination curves with a marginal breaker.
Trip unit and auxiliary contacts — what's inside
The ETU350 is a basic electronic trip with line protection only — no voltage trigger, no undervoltage release, no phase-failure detection, no ground-fault monitoring, and no communication module. It's a straight feeder breaker for a distribution panel, not a motor-protection device. The auxiliary contact block ships as 2 auxiliary switches plus 1 trip alarm switch (HQ designation), so you get separate N/O and N/C for the PLC input and a dedicated alarm contact for the SCADA system. Rated insulation voltage Ui is 800 V, and the maximum power loss at rated current hits 96 W — that's the heat you need to vent inside the enclosure, especially if you're stacking several of these on a common bus. Latching endurance is rated at 15,000 operations, which is standard for a fixed-mount MCCB in a distribution role.
Physical fit and environmental limits
Dimensions are 248 mm high by 138 mm wide by 110 mm deep — a standard 3-pole MCCB footprint for a 400 A SENTRON frame. The front face carries an IP40 rating, so it's dust-protected but not sealed against hose-down; mount it inside a panel, not on the wet side of the wall. Operating range is -25 °C to 70 °C, storage from -40 °C to 80 °C.