What this 400 A SENTRON MCCB is and what it does
The Siemens 3VA2340-7HN32-0JA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in industrial power distribution. It is a 3-pole unit rated for 400 A continuous current at 40 °C, meaning it can carry that load indefinitely without tripping under normal conditions — a key figure for sizing the main feeder or large motor branch circuit. The interrupting capacity tells you what fault it can clear: 330 kA at 240 V AC, 242 kA at 415 V and 440 V, 187 kA at 500 V, and 7.5 kA at 690 V. At the common 400 V-class industrial voltage (415 V), the 242 kA rating means this breaker can safely interrupt a fault up to that level without catastrophic failure — a critical parameter for high-fault-current installations like transformer secondaries or large motor control centers. A shunt trip release (STL) is fitted as the auxiliary release, allowing remote tripping via a control signal — useful for emergency-stop circuits or interlocking with upstream protection. There is no undervoltage release and no ground-fault monitoring on this variant.
Current derating and thermal limits
The 400 A rating holds at 40 °C, 45 °C, and 50 °C. Above that, derating applies: 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, and 340 A at 70 °C. If this breaker lives in a hot enclosure — near other heat sources or in a non-ventilated panel — use the derated value for your load calculation, not the 400 A nameplate. Maximum power loss is 96 W. That is the heat the breaker dumps into the panel at full rated current. Factor it into your enclosure thermal budget, especially if multiple breakers are ganged. Operating ambient range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage limit governs handling and warehousing, not running conditions.
Panel fit and dimensions
Dimensions: 248 mm height, 138 mm width, 110 mm depth. This is a standard MCCB footprint for the 400 A frame class. The 110 mm depth (4.33 in) is the dimension that matters for enclosure depth clearance — verify it clears the door or deadfront when mounted on a DIN rail or backplate.