400 A MCCB with ETU560 — line protection for high-fault panels
The Siemens SENTRON 3VA2340-5JQ32-0KA0 is a 3-pole molded case circuit breaker rated 400 A continuous current at 40 °C, with a maximum interrupting capacity of 187 kA at 240 V AC. That interrupting rating means it can safely clear a fault up to 187 kA without the arc flash propagating upstream — critical for switchboards close to the transformer secondary where available fault current is high. The breaker carries the ETU560 electronic trip unit, which provides adjustable long-time, short-time, instantaneous, and ground-fault protection curves. The integrated shunt trip (STL) allows remote tripping from a PLC or emergency-stop circuit, and the communication function supports integration into a monitoring system — useful for a plant floor where you want to log trip events or reset remotely. Rated insulation voltage is 800 V, so it's suitable for 480 V and 600 V class systems with margin. The 3VA2340 frame is built for line protection (not just feeder), meaning it's the primary overcurrent device for a bus or a large motor control center.
Thermal derating and panel fit
The breaker holds 400 A continuously up to 50 °C ambient. Above that, it derates: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. If your panel runs hot — near a furnace line or in a non-conditioned electrical room — factor that derating into your load calculation. Dimensions are 248 mm high, 138 mm wide, 110 mm deep. The 138 mm width is a standard 3-pole MCCB footprint for this frame size, so it drops into a SENTRON 3VA panelboard or a DIN-rail mounting base without surprises. The 110 mm depth leaves room for rear-connection bus bars in a typical 600 mm deep enclosure. Power loss at full load is 96 W maximum. That's not trivial — if you're packing multiple breakers in a closed cabinet, add up the heat and check your ventilation or forced-air cooling.