What this MCCB does on the line
The Siemens 3VA2340-5HM32-0AA0 is a SENTRON molded case circuit breaker rated for 400 A continuous current, 3-pole, designed for line protection. It handles fault currents up to 187 kA at 240 V and 121 kA at 415 V or 440 V — that's the interrupting capacity that clears a bolted fault before the upstream gear takes damage.
Rating so-what for the panel
At 400 A continuous and 800 V rated insulation voltage, this breaker is sized for heavy feeders or large motor branch circuits in industrial switchboards. The 3-pole form factor fits standard MCCB mounting footprints. Ground-fault monitoring via summation current formation on the L-conductor means it can detect leakage without a separate GFCI module — useful on grounded-wye systems where you want to trip on ground fault without adding hardware.
Thermal derating matters in a hot panel
The 400 A rating holds up to 50 °C ambient; above that it derates linearly — 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, and 340 A at 70 °C. Operating temp range is -25 °C to 70 °C, storage from -40 °C to 80 °C. If your panel runs hot near a drive or transformer, you need to account for that drop. Max power loss is 96 W, so ventilation matters in a sealed enclosure.