What the ratings mean for fit
The Siemens SENTRON 3VA2340-5JQ42-0AJ0 is a 4-pole molded case circuit breaker rated 400 A continuous at 40 °C, with a maximum interrupting capacity of 187 kA at 240 V AC. That 187 kA figure means it can safely clear a fault current up to that level without rupturing — critical for high-fault installations like large transformer secondaries or busway taps. At 415 V and 440 V the interrupting rating drops to 121 kA, and at 690 V it falls to 7.5 kA, so the voltage class of your distribution system directly governs whether this breaker is the right choice. The 400 A rating holds steady through 50 °C; above that it derates linearly to 300 A at 70 °C, which matters if the breaker lives in a hot enclosure or near other heat sources. This is a line-protection design (not motor or generator protection), so the trip curve and accessories are optimized for feeder and main breaker duty. The unit includes a communication function for integration into a monitoring or energy-management system, plus two auxiliary switches and one trip alarm switch — enough for status feedback to a PLC or SCADA without an external interface module.
Panel integration and mounting
Dimensions are 248 mm high, 184 mm wide, 110 mm deep — a standard SENTRON 3VA2 frame footprint. It mounts on a DIN rail or can be bolted directly to a backplate. The 110 mm depth leaves room for rear-access wiring in a typical 600 mm deep enclosure. Four poles mean it needs four line and four load conductors; plan your gland plate and busbar layout accordingly.
Thermal management and power loss
Maximum power loss is 96 W at rated current. That is not trivial — in a sealed, uncooled panel the heat adds up. If you are packing multiple breakers in a small enclosure, factor the 96 W into your thermal calculation to avoid nuisance tripping from ambient rise. The breaker itself is rated for operation from -25 °C to 70 °C, but the enclosure ambient is what drives the derating curve.