400 A MCCB with ETU550 — interrupting curve and thermal derating
The Siemens SENTRON 3VA2340-5JP32-0DF0 is a 3-pole molded case circuit breaker rated for continuous current of 400 A at 40 °C through 50 °C. Above 55 °C the rating steps down: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C — so if the panel ambient runs above 50 °C, size for the derated value, not the nameplate. The ETU550 electronic trip unit gives adjustable long-time delay (tr 0.5–17 s) and short-time delay (tsd 0.05–0.5 s), letting you coordinate selectively with downstream breakers. Interrupting capacity varies sharply with line voltage: 187 kA at 240 V, 121 kA at 415 V, 55 kA at 440 V, 36 kA at 500 V, and 7.5 kA at 690 V. At 415 V it handles 121 kA — that covers most industrial secondary-distribution fault levels. The 690 V figure (7.5 kA) is the weak corner; if your system runs 690 V with high available fault current, this breaker may need an upstream current limiter.
Panel fit and enclosure sealing
Footprint is 138 mm wide (5.4 in), 248 mm tall (9.8 in), 110 mm deep — a standard 3-pole MCCB envelope. Front face carries IP40 protection, so it is fine in a clean indoor panel but not washdown-rated; keep it behind a sealed enclosure door if the environment is wet or dusty.