400 A MCCB with motor protection — what the ratings mean for your panel
The Siemens 3VA2440-5MN32-0CL0 is a 3-pole SENTRON molded case circuit breaker rated for 400 A continuous current across the full 40 °C to 70 °C ambient range — no derating needed up to that ceiling, which simplifies panel layout in warm enclosures or near heat sources. Breaking capacity sits at 121 kA at 415 V and 187 kA at 240 V, dropping to 75.6 kA at 500 V and 9 kA at 690 V — this covers most industrial distribution fault levels downstream of a transformer, but at 690 V the short-circuit capability is limited, so verify the available fault current if you're feeding a 690 V bus. Designed specifically for motor protection, with phase failure detection built in and an undervoltage release (UVR) fitted as standard — the UVR drops the breaker if supply voltage falls below the dropout threshold, preventing a motor from re-accelerating into a stalled load after a dip.
Panel fit and auxiliary wiring
Dimensions are 248 mm high, 138 mm wide, 110 mm deep — a standard MCCB footprint that fits most DIN-rail or panel-mount enclosures without gland-plate rework. The auxiliary switch block includes 2 auxiliary switches, 1 trip alarm switch, and 1 electrical alarm switch (HQ type) — enough for remote status indication on a PLC input card and a separate alarm circuit without adding a second module. Power loss is 66 W maximum at rated current — account for this in enclosure thermal calculations if the breaker is grouped with other heat sources.