What this MCCB delivers
The Siemens SENTRON 3VM1340-4ED32-0AA0 is a 3-pole molded case circuit breaker rated for 400 A continuous at 40 °C, designed for line protection in distribution panels. It carries a TM210 thermal-magnetic release — the '210' indicates the fixed thermal pickup at 210% of the rated current, meaning the thermal trip initiates between 400 A and 840 A depending on overload duration, while the magnetic short-circuit trip acts instantaneously above a factory-set threshold. This is a standard MCCB for feeder or main breaker duty in commercial and industrial switchboards. Interrupting capacity is strong: 121 kA at 240 V AC, 76 kA at 415 V AC and at 440 V AC, and 53 kA at 500 V AC. That 76 kA at 415 V is the figure most European 400 V-class installations care about — it tells you this breaker can clear a bolted fault at the main bus without rupturing, provided the available fault current at the installation point stays under that rating. For DC systems, Siemens directs you to the 3VA Molded Case Circuit Breaker Manual for the specific DC switching capacity values.
Thermal derating and panel fit
The 400 A rating holds from 40 °C up to 50 °C ambient. Above that, the continuous current must be reduced: 392 A at 55 °C, 384 A at 60 °C, 376 A at 65 °C, and 367 A at 70 °C. If your panel ambient runs hot — say a non-air-conditioned electrical room in a tropical plant — size the upstream conductor and downstream bus for the derated value, not the nameplate 400 A. The breaker itself dissipates up to 92 W at full load, which contributes to the enclosure heat rise. Dimensions are 248 mm high, 138 mm wide, 110 mm deep. That 110 mm depth is the body only — add clearance for the arc chute exhaust and cable bending radius at the line and load lugs. The front face carries an IP40 protection class, meaning it's protected against tools and wires >1 mm but not against water ingress; mount it inside a suitable enclosure in washdown areas.