50 A D-curve MCB for motor and transformer branch circuits
The Siemens 5SY7450-8CC is a 4-pole SENTRON miniature circuit breaker with a D tripping characteristic rated at 50 A at 400 V AC. The 15 kA breaking capacity per IEC 60947-2 means it safely clears a fault up to that level without upstream fuses needing to open first; the 5 kA rating per UL 1077 covers North American panelboard applications.
Mounting position is any orientation. Combined terminals top and bottom accept solid or stranded conductors from 0.75 to 35 mm². Tightening torque for the screw terminals is 2.5 to 3.5 N·m. Ambient temperature range is -25 to +55 °C operating, with storage from -40 to +75 °C.
The 15 kA rated short-circuit capacity at 400 V AC (IEC 60947-2) allows this MCB to be used as the main branch protector in sub-distribution boards where fault levels are moderate. For higher fault currents, upstream backup fusing or a higher-rated MCCB is required. The D-curve ensures selectivity with downstream C-curve MCBs on most motor-start profiles, but coordination should be verified against the specific load's inrush duration.