Railway-rated MCB with B-curve and 10 kA breaking capacity
The Siemens 5SY5125-6CC11 is a 1-pole miniature circuit breaker rated 25 A with a B-curve trip characteristic, delivering a 10 kA breaking capacity at both 230/400 V AC and 220 V DC. This is a railway-classified unit — the 220 V DC rating and the 10 kA SCCR make it suitable for DC auxiliary circuits in rolling stock and wayside equipment, not just standard AC panelboard duty.
Voltage rating and DC capability
Rated for 230/400 V AC and 220 V DC — the DC rating is the key differentiator here. Most standard B-curve MCBs top out at 48–60 V DC; this one handles 220 V DC at the full 10 kA breaking capacity, which means it can protect DC bus feeds, battery circuits, and signalling supplies in railway environments without needing a series-connected second pole.
Listed as current production. No official successor or cross-reference.