What this 400 A MCCB delivers — and the decisions it drives
The Siemens SENTRON 3VA2340-6KP32-0AE0 is a 3-pole molded case circuit breaker rated for 400 A continuous current, fitted with an ETU850 electronic trip unit. At 240 V it interrupts 242 kA — that's the short-circuit withstand you need for high-fault utility feeds or transformer secondaries. The trip unit is programmable and the breaker carries a communication function, so it integrates into a power-monitoring or selective-coordination scheme rather than sitting as a standalone thermal-magnetic device.
Breaking capacity across voltages — where the 242 kA matters
The interrupting ratings drop as voltage rises: 242 kA at 240 V, 187 kA at both 415 V and 440 V, 121 kA at 500 V, and 40 kA at 690 V. That 40 kA at 690 V is still a solid figure for a 400 A frame — it clears faults on 690 V industrial networks without cascading to upstream gear. The 187 kA at 415 V covers most European and Asian distribution panels where the service transformer is sized for high fault current.
Thermal derating — the real-world current you can carry
This breaker holds its full 400 A rating 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 the panel ambient runs hot — say a non-climate-controlled enclosure near a furnace line — the 300 A at 70 °C figure is the one to size against. The operating range spans -25 °C to 70 °C, with storage from -40 °C to 80 °C.
Panel fit — dimensions and integration
The breaker measures 248 mm tall, 138 mm wide, and 110 mm deep — a standard 3-pole MCCB footprint that fits most SENTRON mounting plates and switchboard chassis. The 110 mm depth is the installed projection from the mounting surface, so verify clearance to the enclosure door or busbar shroud. Four HQ auxiliary switches are factory-integrated; no separate aux block to wire in the field.