What this 4-pole MCB does in the panel
The Siemens 5SN6425-8CP is a 4-pole miniature circuit breaker from the SENTRON 5SN family, rated for 400 V AC at 50 Hz and 72 V DC.
The 6 kA rating under EN 60898 covers standard building-installation fault levels; the 15 kA under IEC 60947-2 is the one to use when designing for industrial SCCR headroom — it tells you the breaker can interrupt a 15 kA prospective fault without welding its contacts. At 440 V AC multi-phase operation, it handles the upper end of a 400 V class supply (typical tolerance band). The 2.1 W power loss per pole at rated current in hot state matters for thermal coordination inside a crowded enclosure — four poles dissipate 8.4 W total, which is modest and unlikely to force derating in a standard 4-MW-wide DIN-rail slot.
Panel integration and mechanical fit
Snap-on DIN-rail mounting, 4 modular width units (72 mm wide), 90 mm tall, 76 mm deep with a 70 mm installation depth. Accepts solid conductors up to 35 mm² — enough for the outgoing feeder on a 40 A class circuit. The -40 °C to 75 °C operating range covers unheated electrical rooms and outdoor enclosures in temperate climates.