What it is and what it does
The Siemens SENTRON 3VA2440-5MN32-0AC0 is a 3-pole molded case circuit breaker (MCCB) designed specifically for motor protection — that means it's built to handle the high inrush and overload profile of a motor circuit, not just a distribution feeder. It carries a continuous 400 A from 40 °C all the way up to 70 °C without derating, which is unusual and tells you the thermal design has headroom for a warm panel or a tight enclosure. Breaking capacity is the number that decides whether this breaker holds or vents on a hard fault. At 240 V it's rated 187 kA, at 415/440 V it's 121 kA, at 500 V it's 75.6 kA, and at 690 V it drops to 9 kA. That 121 kA at 415 V is a serious number — it means this breaker can sit downstream of a large transformer or a high-fault bus without needing a current-limiting upstream device in most industrial installations. Phase failure detection is built in, which is a standard expectation on a motor-protection breaker but worth confirming — some general-purpose MCCBs skip it and rely on the overload relay. Here the breaker itself watches for a lost phase and trips, which saves a motor from single-phasing.
Panel fit and integration
Dimensions are 248 mm high, 138 mm wide, 110 mm deep. That's a standard SENTRON 3VA frame size for a 400 A 3-pole — it bolts into a panel on a mounting plate, not a DIN rail. The 110 mm depth is shallow enough that it clears most 200 mm deep enclosures with room for rear-connected busbars or a back panel. It ships with 2 auxiliary switches HQ and the supplied basic switch is 3VA2440-5MN32-0AA0. No undervoltage release, no voltage trigger, no communication module — it's a standalone motor-protection breaker with aux contacts for status feedback to a PLC or annunciator. Maximum power loss is 63.5 W. That's the heat it dumps into the enclosure at full rated current — factor that into your thermal calculation if the panel is sealed or has limited ventilation.