The Siemens 5SY6325-8CC is a SENTRON miniature circuit breaker — 3-pole, D-curve, 25 A, rated 6 kA per EN 60898 at 400 V AC. Under UL 1077 and CSA C22.2 No. 235 it's rated 5 kA — a useful cross-reference if the job spec calls for North American supplementary protection rather than the IEC branch-circuit standard. The 25 A rating is the continuous current at 40 °C ambient; above that, the thermal curve derates per the surrounding-temperature influence table (max 95% RH at 55 °C, dropping to 35% at 75 °C).
Three modular-width units (54 mm wide) on a standard DIN rail.
D-curve selection context
The D-curve is the least sensitive of the standard MCB characteristics — magnetic trip between 10× and 20× In. For a 25 A MCB, that means the magnetic element won't operate below about 250 A instantaneous, and may hold up to 500 A for a few milliseconds. That's deliberately slow to ride through the starting surge of a 7.5 kW motor or the magnetizing inrush of a 400 VA control transformer. If the load is resistive (heaters, lighting) or has a low inrush, a C-curve would trip faster and give better selectivity; the D-curve is the right call only when you need the headroom.