What it is and what the ratings mean
The Siemens 5SU1646-6FP06 is a 4-pole RCBO (residual current circuit breaker with overcurrent protection) from the SENTRON family, combining a B-curve miniature circuit breaker and a Type A residual current device in one 4-module-wide unit. Rated In 6 A with a 6 kA breaking capacity at 400 V, it protects final circuits against both overload/short-circuit and earth leakage. The 300 mA residual sensitivity and Type A detection mean it catches pulsating DC fault currents common on single-phase rectified loads — think switched-mode power supplies, LED drivers, or VFD-fed equipment. B-curve characteristic (3-5 In magnetic trip) suits resistive and light inductive loads like lighting circuits, small heaters, or control transformers.
Where it fits in the panel
Snaps onto standard 35 mm DIN rail in a distribution board or sub-distribution panel. At 4 modules wide (roughly 72 mm), it occupies the same footprint as a 4-pole MCB plus a separate RCD — but in one package, saving one DIN position and reducing wiring. The 96 x 40 x 82 mm envelope fits alongside other SENTRON 5SU series devices for clean busbar or comb-bridge feeding. Rated 400 V line-to-line, so it goes on a 3-phase 4-wire system (-L2-L3-N) with the neutral switched internally.