RCD / RCBO for motor and pulsed-load circuits
The Siemens SENTRON 5SU9354-8KK50 is a 2-pole (1P+N) RCD-operated circuit breaker — essentially an RCBO — rated 50 A with a D tripping characteristic and Type A fault-current sensitivity. The D curve (10–20× In magnetic trip) makes it a natural fit for motor starters, small drives, and pulsed loads where a B or C curve would nuisance-trip on inrush. Type A detection catches pulsating DC fault currents from single-phase rectifiers, so it covers VFD front-ends and switched-mode supplies that a plain AC-sensitive RCD would miss. Breaking capacity is 10 kA per both EN 60898 and IEC 60947-2, which covers the majority of sub-distribution boards in commercial and light industrial panels.
Mounting and wiring constraints
Width is 36 mm (2 MW), depth 77 mm, installation depth 70 mm. Accepts solid or stranded copper up to 35 mm² — enough for the 50 A feed. Supply can enter from top or bottom, and mounting position is any orientation, which simplifies panel layout in tight enclosures. Touch protection is built in (IP20 with distribution board installed and conductors connected). Halogen-free and silicon-free construction matters if the panel sits in a clean-room or food-processing environment where outgassing contaminates product.
Thermal derating and ambient limits
The 50 A rating holds at 30 °C ambient. At 40 °C it derates to 47 A, at 45 °C to 45.5 A, at 50 °C to 43.5 A, and at 55 °C to 40.5 A. If the panel runs warm — say next to a drive or transformer — factor that derating into the load schedule. Ambient operating range is -25 to +45 °C; storage range is -40 to +75 °C.