The Siemens SENTRON 5SM3444-6LB01 is a 4-pole RCCB, Type A, short-time delayed, rated at 40 A and 100 mA tripping residual current on a 400 V AC supply.
Type A fault current detection means it catches pulsating DC residual currents from rectifiers and switching power supplies — common on modern industrial panels with VFDs or SMPSs. The short-time delayed characteristic (3 kA surge current resistance) prevents nuisance tripping from transient surges or inrush, so it's suited for circuits with motor starts or capacitive loads where a standard RCCB would drop out. Overvoltage category III confirms it's rated for fixed-installation distribution boards, not just downstream equipment. Terminals accept 1.5 to 25 mm² solid or stranded copper, with a tightening torque of 2.5 to 3 N·m.
Panel integration
Snaps onto DIN rail (REG), occupies 4 width units, and installs 70 mm deep into the enclosure. Mounting position is any. Supply can land top or bottom; the test circuit needs a minimum of 100 V AC to function. The screw terminals are finger and back-of-hand safe per the shock protection class, so panel builders don't need bootlace ferrules for safe handling during commissioning.