400 A MCCB with 121 kA interrupting capacity
The Siemens 3VA1340-4EF32-0KA0 is a SENTRON molded case circuit breaker rated for 400 A continuous current across three poles, with a maximum breaking capacity of 121 kA at 240 V. That interrupting rating drops to 76 kA at 415 V and 440 V, then to 53 kA at 500 V, and 10.5 kA at 690 V — enough headroom for most industrial distribution panels where the available fault current is known and the SCCR needs to be coordinated upstream. The 15000-cycle latching endurance matches the duty cycle of a main feeder breaker that sees infrequent switching; it is not rated for daily motor-start duty.
The 400 A rating holds flat from 40 °C to 50 °C ambient. Above that it derates: 392 A at 55 °C, 384 A at 60 °C, 376 A at 65 °C, 367 A at 70 °C. If the enclosure runs hot — say a non-ventilated panel near a furnace line — that 367 A at 70 °C figure is the one to size against, not the nameplate 400 A. Dimensions are 248 mm high, 138 mm wide, 110 mm deep. The 138 mm width is a standard 3-pole MCCB footprint for 400 A frame sizes — it fits Siemens 3VA switchboard mounting bases and most DIN-rail adapters without panel modifications. Rated insulation voltage is 800 V, so it handles 480/277 V and 600 V systems with margin.
Maximum power loss is 92.1 W at rated current — a consideration for thermal management inside a sealed enclosure. Operating temperature range is -40 °C to 70 °C; storage range is -40 °C to 80 °C.