The Siemens SENTRON 3VA2440-7KQ32-0AA0 is a 3-pole molded case circuit breaker (MCCB) rated for 400 A continuous current (Iu) at 40–50 °C, with a 400 A frame that holds the full rating up to 50 °C before derating begins — at 55 °C it carries 376 A, at 60 °C 352 A, at 65 °C 324 A, and at 70 °C 300 A. That thermal curve means a panel designer running a 400 A feeder in a 50 °C enclosure gets full capacity; above that, the breaker self-protects by reducing the continuous rating, not by nuisance tripping. Breaking capacity is the headline: 330 kA at 240 V, 242 kA at 415 V and 440 V, 187 kA at 500 V, and 9 kA at 690 V.
That 138 mm width (roughly 5.4 in) is the standard 3-pole MCCB footprint for the SENTRON 3VA platform — it occupies the same horizontal slot as other 3VA 3-pole breakers, so a panel designed for a 250 A frame can accept this 400 A unit without re-drilling the mounting plate. Depth at 110 mm (4.3 in) keeps the breaker within typical switchboard gut depths.