What this 400 A MCCB delivers — and where the ratings matter
The Siemens SENTRON 3VA2440-5HK32-0AA0 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 simplifies panel sizing: you do not have to over-spec the frame just because the enclosure sits near a warm drive bay. Breaking capacity is the headline. This unit clears 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 9 kA at 690 V. Those numbers cover most low-voltage distribution panels in North America (480Y/277 V) and Europe (400 V). The 9 kA at 690 V still handles industrial motor-drive circuits at that voltage. Short-time withstand is 5 kA for 1 s, which matters when you need the breaker to ride through a momentary fault while a downstream device clears. If you need those, you are looking at a different order-code suffix.
That 138 mm width (5.43 in) fits standard 3-pole MCCB cutouts in most switchboard and panelboard layouts. Depth of 110 mm (4.33 in) leaves room for rear bus connections and cable bending radius in a 300 mm deep enclosure. Mounting is via the four-bolt pattern typical of SENTRON 3VA frames — no DIN-rail adapter on this size. Maximum power loss is 63.5 W at rated load. That is not trivial in a sealed enclosure — account for it in thermal calculations.