DC miniature circuit breaker for railway and industrial DC branches
The Siemens SENTRON 5SY5240-7CC11 is a 2-pole DC miniature circuit breaker rated for 440 V DC with a 10 kA breaking capacity per IEC 60947-2. The C tripping characteristic (5–10× In) handles moderate inrush from DC motor drives, solenoid valves, and control transformers common in railway auxiliary circuits. Designed for railway applications, it carries vibration resistance per IEC 60068-2-6 (50 m/s² at 25–150 Hz) and operates across -40 to 75 °C ambient. The 36 mm width (2 modular units) snaps onto a DIN rail via the quick assembly system, with any mounting position allowed.
DC rating and breaking capacity — what they mean for fit
The 440 V DC rated voltage and 10 kA breaking capacity (IEC 60947-2) define the fault-clearing envelope. For a 440 V DC bus, this breaker can interrupt a short-circuit up to 10 kA without welding contacts or cascading failure upstream. The C-curve means magnetic trip occurs between 5 and 10 times rated current — suitable for loads with a moderate inrush peak, such as DC-DC converters or contactor coils. Temperature derating is published from 40 °C (37.76 A) through 75 °C (no current listed at that extreme, but the pattern continues); for a 40 °C panel, the breaker carries its full rated current. The 2-pole design switches both lines in a DC circuit, and polarity must be observed per the marking on the supply side.