The 5SV3346-6MJ01: Type A detection means it responds to both sinusoidal AC residual currents and pulsating DC residual currents — the kind that come from single-phase rectifiers in switched-mode power supplies, VFDs, or LED drivers. If your downstream loads include electronics with rectifier front ends, a Type A is the minimum you need; a plain Type AC would miss the pulsating DC component.
This is a DIN-rail mounted unit for standard 35 mm rail. The 3+N-pole body occupies four module widths (4 MW per the description). In a distribution board, it sits downstream of the main breaker or upstream of individual MCBs on the outgoing circuits. The short-time-delayed 'G' characteristic makes it suitable for sub-mains protection where you need selectivity with downstream instantaneous RCDs — the G type's delay lets the downstream device clear a fault first, avoiding a whole-board blackout for a single branch fault.