The Siemens SENTRON 5SQ2270-0KA40 is a 2-pole miniature circuit breaker rated for 40 A at 400 V AC, with a C tripping characteristic and a 3 kA breaking capacity per EN 60898. It also handles DC circuits (type of voltage AC/DC). This is the part for a 40 A branch circuit needing a C-curve — the magnetic trip holds through moderate inrush (motor starts, capacitor banks, transformer energization) and clears on sustained overload.
Snaps onto standard DIN rail. Occupies 2 width units (about 36 mm) and has an installation depth of 55 mm — shallow enough for most flush-mount enclosures. IP20 rated, so it belongs inside a closed distribution board or panel, not in a wet or dusty location. Neutral conductor switching is integrated (product function / neutral conductor switching = Yes), which simplifies wiring in 2P applications where you want to isolate both phase and neutral.