The Siemens SENTRON 5SY6401-8 is a 4-pole miniature circuit breaker with a D tripping characteristic, rated at 1 A at 400 V AC. The D curve means it tolerates high inrush currents — typically motor starting or transformer energization — without nuisance tripping, but clears a hard fault within the standard time-current envelope. With a 6 kA breaking capacity per EN 60898 and a 30 kA rating per IEC 60947-2, it coordinates with downstream branch protection and upstream distribution panels.
Mounting is via the quick-assembly system — snaps onto DIN rail at any orientation, with a 70 mm installation depth. The 72 mm width (4 width units) fits standard enclosure cutouts. Combined terminals top and bottom accept copper conductors without a separate busbar adapter. Touch protection is built in, and the housing is halogen- and silicon-free, which matters for clean-room or offshore environments where outgassing can contaminate contacts or coatings.