What this MCCB carries and where it fits
The Siemens SENTRON 3VA2340-6JQ32-0JA0 is a 3-pole molded case circuit breaker (MCCB) designed for line protection — meaning it sits at the main feeder or a large subfeed to guard cables and busbars against short-circuit and overload. Its 400 A rating at 40 °C and 242 kA breaking capacity at 240 V tell you it is sized for high-fault industrial switchboards, not a small panel. The shunt trip (STL) auxiliary release allows remote tripping, which is common in emergency-stop circuits or interlocked distribution schemes. Communication function is built in, so it can report status to a BMS or PLC without an add-on module.
Thermal derating — the real-world current
The breaker holds its full 400 A up to 50 °C ambient (–). Above that, it derates linearly: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. If your panel internal ambient runs hot — say a sealed enclosure near a furnace line — you need to size the breaker for the derated value, not the nameplate. The 70 °C operating maximum is the ceiling; storage range is -40 °C to 80 °C (–).
Breaking capacity across voltages
The interrupting rating drops as system voltage rises — standard for any MCCB. At 240 V it clears 242 kA; at 415 V and 440 V it handles 187 kA (–); at 500 V it is 121 kA; at 690 V it falls to 7.5 kA. For a 480 V or 600 V class installation, the 121 kA at 500 V is the relevant figure — still very high, but not the headline 242 kA. The minimum trip setting is 600 A, maximum 4 000 A, so the breaker is adjustable for cable protection coordination.
Physical fit and panel integration
Dimensions are 248 mm high, 138 mm wide, 110 mm deep. That is a standard SENTRON 3VA form factor — it mounts on a backplate or DIN rail via the breaker's own base, not a separate adapter. The 138 mm width means it occupies three 45 mm pole spaces, typical for a 3-pole MCCB in a distribution board. Verify the depth clearance inside the enclosure: 110 mm plus wiring space for the line and load lugs.