What this MCCB is and what the ratings mean for your panel
The Siemens 3VM1340-4EE32-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for line protection in distribution panels. Its 400 A continuous current at 40 °C and 3-pole construction make it a fit for main or large feeder breakers in commercial and industrial switchboards. The TM220 overcurrent release is a thermal-magnetic design — the thermal element handles overloads with an inverse-time curve, and the magnetic element trips instantaneously on short-circuit. The interrupting ratings tell you where it can safely clear a fault: 121 kA at 240 VAC, 76 kA at 415 VAC, and 53 kA at 500 VAC. That 121 kA figure at 240 V means it can handle high available fault current common in North American 240/120 V distribution without needing a current-limiting fuse upstream. The 690 VAC rated operating voltage and 800 V rated insulation voltage confirm it is designed for 400 V and 480 V systems with margin. IP40 on the front means protection against tools and wires larger than 1 mm — standard for enclosed panel mounting, not for washdown areas.
Thermal derating and continuous current across temperature
This breaker holds its full 400 A rating from 40 °C through 50 °C. Above that, it derates: 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 near a furnace line or in a non-conditioned enclosure — you need to account for that derating at the design stage. The maximum power loss is 92 W, which matters for enclosure thermal calculations.
Physical fit and panel integration
Dimensions are 248 mm high, 138 mm wide, and 110 mm deep. That 138 mm width is standard for a 3-pole MCCB in this class — it occupies three 45 mm pole spaces on a DIN rail or panel-mount base. The IP40 front means it is intended for installation inside an enclosure with a door, not exposed to dripping water or hose-down. No undervoltage release and no communication function are built in — this is a straightforward thermal-magnetic breaker, not a smart or remotely tripped unit.