400 A MCCB with starter protection — what the ratings mean for fit
The Siemens SENTRON 3VA2440-7MS32-0AA0 is a 3-pole molded case circuit breaker rated for 400 A continuous current across the full ambient range from 40 °C to 70 °C — no derating needed up to that ceiling. That flat thermal curve is unusual; most MCCBs start pulling back above 40 °C. Here it means the 400 A nameplate holds in a warm panel or next to a motor starter without recalculating the load. Breaking capacity is 330 kA at 240 V, 242 kA at 415 V and 440 V, 187 kA at 500 V, and 9 kA at 690 V. Those numbers are the SCCR the breaker can interrupt without welding or rupturing — critical for high-fault utility feeds or transformer secondaries. At 415 V the 242 kA rating covers most industrial service-entrance duty; the 9 kA at 690 V is the ceiling for that voltage class. The product is explicitly designed for starter protection — meaning it coordinates with a contactor and overload relay to clear motor faults while letting the overload handle running overloads. That design intent makes it a natural fit for motor control center buckets or individual motor branch circuits where you want the MCCB to act as the backup, not the primary trip.
Panel fit and physical integration
Dimensions: 248 mm height, 138 mm width, 110 mm depth. That 110 mm depth is the key clearance number for shallow enclosures or gland-plate clearance — measure the back-of-panel depth before committing. The 138 mm width is the standard 3-pole MCCB footprint for this SENTRON frame; it fits the same DIN-rail or mounting-plate cutout as other 3VA 3-pole units. Rated insulation voltage is 800 V. Maximum power loss is 63.5 W.