MCCB for motor branch circuits — 400 A, 3-pole, with undervoltage release
The Siemens SENTRON 3VA2440-5MN32-0CA0 is a 3-pole molded case circuit breaker (MCCB) rated 400 A continuously across the full 40 °C to 70 °C ambient range — no derating needed up to that ceiling. Breaking capacity sits at 121 kA at 415 V and 187 kA at 240 V, giving solid fault-clearing headroom on a 400 V distribution bus. The design is explicitly for motor protection and includes integrated phase failure detection, so it handles the inrush and overload profile of a motor branch circuit without nuisance trips. An undervoltage release (UVR) is built in, which means the breaker drops the load automatically if supply voltage falls below the release threshold — a standard requirement for safety interlocks on conveyors, pumps, and compressors.
That means this breaker can be packed into a warm enclosure or mounted near heat-producing drives without losing ampacity. At 690 V the breaking capacity drops to 9 kA, so on a 690 V system the breaker is limited to low-fault branches. The limited-to-1-second rating of 5 kA governs short-time withstand for selective coordination — downstream breakers must clear faster than 1 s or the 3VA2440 trips.
The 66 W maximum power loss needs to be factored into enclosure thermal calculations; at full load the breaker dissipates roughly the heat of a small soldering iron. The undervoltage release is factory-installed; no auxiliary switch is present, so if you need remote status indication, order the auxiliary switch variant or add one externally.