What it is and what it does
The Siemens SENTRON 3VA2340-7KP32-0AA0 is a 3-pole molded case circuit breaker (MCCB) rated for 400 A continuous current at 40 °C, with an ETU850 electronic trip unit. It's the line protection version — meaning it's configured for feeder and main breaker duty, not motor circuit protection. The 400 A rating holds steady from 40 °C up to 50 °C, then derates to 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. That thermal curve matters if you're stuffing this into a hot panel — the 400 A nameplate is only good if your enclosure ambient stays under 50 °C. Breaking capacity runs 330 kA at 240 V AC, 242 kA at 415 V and 440 V, 187 kA at 500 V, and 7.5 kA at 690 V. That's a lot of fault current muscle at the lower voltages — typical for a main breaker on a large secondary substation or a high-capacity industrial feeder. At 690 V the 7.5 kA figure is the limiting case; if your system voltage sits there, verify the available fault current stays under that ceiling.
Panel fit and integration
Dimensions are 248 mm tall, 138 mm wide, 110 mm deep. That 138 mm width is the standard 3-pole MCCB footprint for this SENTRON frame size — it'll land on the same mounting pattern as other 3VA2 breakers in the same frame class. The IP40 front protection means it's fine for a closed panel; no special gasketing needed for the switch handle opening. The ETU850 trip unit supports communication and other measurement functions — so this breaker can talk to a higher-level monitoring system via the SENTRON communication modules. Neutral protection is adjustable from OFF to 20%–160% of the phase current setting. That's useful on 4-wire systems where you need to protect the neutral against harmonic currents.