What this 400 A MCCB carries — and where the rating matters
The Siemens 3VA2340-5KP32-0KH0 is a SENTRON molded case circuit breaker rated for 400 A continuous current (Iu) with a 3-pole configuration, sized for main feeder or large motor branch protection in industrial distribution panels. The ETU850 electronic trip unit gives you adjustable long-time, short-time, instantaneous, and ground-fault curves — not a fixed thermal-magnetic, so coordination studies actually stick. Breaking capacity climbs to 187 kA at 240 V and holds 121 kA at 415 V and 440 V, then drops to 75.6 kA at 500 V and 17 kA at 690 V; that 121 kA at 415 V is the number to check against your transformer fault current. Thermal derating starts at 55 °C: the breaker holds full 400 A up to 50 °C, then steps down to 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. If your panel ambient runs toward 60 °C, you lose 50 A of headroom — factor that into the feeder sizing. Rated insulation voltage Ui is 800 V. The shunt trip (STL) design of the auxiliary release allows remote tripping from an E-stop or PLC output.
Panel fit and integration
Mounts on a DIN rail or direct-panel via the 138 mm width × 248 mm height footprint. Depth of 110 mm leaves room behind the gland plate for cable bending radius on 400 A lugs. The auxiliary contact version carries 2 auxiliary switches plus 1 trip alarm switch (HQ type) — enough for a remote status signal and a separate alarm to the PLC without a dedicated interface relay. Maximum power loss is 96 W at rated current. That heat has to leave the enclosure — if this sits in a multi-breaker lineup, calculate the cumulative dissipation against your panel cooling. The 15 000-cycle latching endurance tells you it's built for occasional switching, not daily motor starting.