DC-rated MCB for 440 V rail systems
The Siemens 5SL5250-7RC is a 2-pole miniature circuit breaker rated for 440 V DC with a 10 kA breaking capacity and a C-curve trip characteristic at 50 A. This is a DC-specific device, not a standard AC MCB — the arc extinction and contact gap are designed for DC commutation, which matters when protecting battery banks, rectifier outputs, or DC bus feeds in industrial control panels. At 50 A rated current it covers a 10–15 kW DC load at 440 V, typical for a string of power supplies or a section of a DC distribution board.
Integration into a DC distribution panel
The 2-pole form factor occupies two DIN-rail module widths (36 mm). Terminals accept 0.5–25 mm² conductors, and the busbar comb can be fed from either pole. For DC applications, both poles must be switched — the 5SL5250-7RC breaks both lines simultaneously, which is required by IEC 60947-2 for DC isolation. Coordination with upstream fuses or a larger MCCB should be verified per the selectivity tables in the Siemens 5SL application manual.