The Siemens SENTRON 5SM3344-6LA01 is a 4-pole residual current circuit breaker (RCCB) rated 40 A at 400 V AC, with a 30 mA trip threshold and Type A fault current sensitivity. It includes built-in thermal overload protection and a short-time delayed switching function, meaning it withstands brief inrush or surge currents without nuisance tripping — useful on circuits feeding motor drives or switching power supplies that draw a momentary charge pulse.
The 30 mA residual trip covers personnel protection (hand-to-hand or hand-to-ground fault paths) per IEC 60364. Type A detection catches pulsating DC fault currents from rectifiers and single-phase drives — a step above plain AC-sensitive Type AC units. The short-time delay (typically 10 ms) provides selectivity with downstream 30 mA instantaneous RCCBs, so a fault on a branch trips the branch device, not this upstream main. The 40 A continuous rating and 400 V line-to-line voltage suit a 3-phase sub-distribution board feeding mixed lighting, socket, and small-motor circuits.
Snaps onto DIN rail (REG profile) and occupies 4 width units (roughly 72 mm at 18 mm per unit). Installation depth is 70 mm — fits standard distribution boards. Terminals accept solid or stranded conductors from 1.5 mm² up to 25 mm², tightened to 2.5–3 N·m. The housing is IP20 once the distribution board is closed and conductors are connected; finger and back-of-hand safe per the protection class. Ambient range is -25 to +45 °C; storage range -40 to +75 °C.