RCCB for selective earth-fault protection
The Siemens SENTRON 5SV3344-4KK14 is a 4-pole residual current circuit breaker (RCCB) rated 40 A with a 30 mA trip threshold, Type B+ characteristic, and short-time delayed switching — meaning it tolerates brief earth-leakage surges (e.g., from VFDs or UPS filters) without nuisance tripping, while still clearing a sustained fault. Type B+ detects smooth DC residual currents up to 1 kHz, so it's the correct choice for circuits feeding frequency converters, rectifiers, or EV chargers where standard AC/DC-sensitive RCCBs would miss the fault. Rated Un AC 400 V, it sits on a 60 mm grid DIN rail (REG) and occupies 4 modular width units (72 mm wide). The 70 mm installation depth fits standard distribution boards; the IP20 rating applies only with conductors connected and the enclosure closed — treat it as panel-internal only, no washdown exposure.
Fault-clearing and coordination
Short-circuit current rating (SCCR) is 10 kA per IEC 61008-1, with a maximum permissible series fuse short-circuit current of 100 A. That 10 kA figure tells you the device can safely interrupt a fault up to that level without welding contacts or rupturing the case — critical for panel coordination studies. The short-time delay (SIGRES function) allows selectivity with downstream RCCBs: the upstream delayed unit holds during a downstream fault, so only the faulted branch opens. Power loss per pole is 2.5 W at rated current in hot operating state — four poles means 10 W total heat to dissipate inside the enclosure. Factor that into thermal derating if the panel is tightly packed.
Mounting and integration
Snap-on DIN rail (REG) mounting, any orientation. Supply can be connected top or bottom; the SIGRES function (short-time delay) remains active even when the switch is in the off state, so the test circuit stays powered from the top terminals. Grid spacing 60 mm aligns with standard modular panel layouts. Operating temperature range -25 °C to +45 °C; storage -40 °C to +75 °C. Silicon-free construction matters for automotive or aerospace panels where silicone outgassing can contaminate contacts or optics.