What this MCCB delivers — and where the ratings matter
The Siemens SENTRON 3VA2340-5HN32-0JH0 is a 3-pole molded case circuit breaker rated for 400 A continuous current at 40 °C, with a maximum breaking capacity of 187 kA at 240 V AC — that's the headline figure for high-fault utility feeds or transformer secondaries where available fault current can exceed 100 kA. At 415 V and 440 V it still holds 121 kA, and at 500 V it delivers 75.6 kA, so it covers most industrial distribution voltages without needing a current-limiting upstream device. The 690 V rating drops to 7.5 kA, which is typical for a 400 A frame at that voltage — fine for motor circuits on 690 V systems where the transformer impedance limits fault current. This is a line-protection design, meaning the trip curve and thermal-magnetic or electronic trip unit are set for cable and busbar protection rather than motor or generator protection. It ships with a shunt trip release (STL) and carries 2 auxiliary switches plus 1 trip alarm switch (HQ) — enough for remote status indication and emergency tripping without adding a separate undervoltage release (none fitted here).
Thermal derating — the real-world continuous current
The 400 A rating holds flat from 40 °C through 50 °C ambient. At 55 °C it derates to 385 A, at 60 °C to 370 A, at 65 °C to 355 A, and at 70 °C to 340 A. If the panel ambient runs above 50 °C — common in sealed enclosures or near furnace lines — size the load at the derated figure, not the nameplate 400 A. The maximum operating temperature is 70 °C; storage range is -40 °C to 80 °C.
Panel fit and footprint
Dimensions are 248 mm high, 138 mm wide, 110 mm deep — a standard 3-pole MCCB footprint for a 400 A frame. The 138 mm width means it occupies three 45 mm pole spaces on a DIN rail or panel-mount plate. Depth of 110 mm includes the arc chamber and terminal clearance; verify gland-plate depth if the breaker mounts near the enclosure back wall. Power loss at rated current is 96 W — account for that in the enclosure thermal calculation.