The SENTRON 5SM3344-6KK01 is a 4-pole Type A residual current circuit breaker (RCCB) rated 40 A at 400 V AC, 50 Hz, with a short-time delayed characteristic. Type A detection covers sinusoidal AC fault currents plus pulsating DC fault currents up to 6 mA smooth DC — the common profile for single-phase rectified loads like switched-mode power supplies, LED drivers, and variable-speed drives. The short-time delayed design (letter K or S in Siemens nomenclature) means it withstands transient leakage without nuisance tripping, making it suitable for circuits with capacitive inrush or downstream soft-starters.
Derating and thermal limits
The 40 A rating holds at ambient temperatures up to 45 °C. Above that, the continuous current must be derated linearly: 38.4 A at 50 °C, 36.8 A at 55 °C, 35.2 A at 60 °C, 33.6 A at 65 °C, and 32 A at 70 °C.
DIN rail integration and panel fit
Snap-on mounting to DIN rail (REG), occupying 4 width units (72 mm). The supply cord position is top or bottom, giving flexibility in busbar routing. Silicon-free construction matters for high-voltage or clean-room adjacent panels where silicone outgassing can contaminate contacts or optics.