The Siemens SENTRON 5SQ2270-0KA04 is a 2-pole miniature circuit breaker with C-curve tripping characteristic, rated 4 A at 400 V AC, 50 Hz.
The 5SQ2270-0KA04 sits in the SENTRON 5SQ family alongside higher-pole siblings. The 4-pole 5SQ2670-0KA15 (15 A, C-curve, 3 kA) shares the same 55 mm depth and IP20 rating — the difference is pole count and current rating. If your BOM calls for a 2-pole 4 A breaker, the 5SQ2270-0KA04 is the direct fit; the 4-pole variant would occupy three width units instead of two and requires a neutral conductor switching path.
Two width units (standard 18 mm per pole) means it takes up 36 mm on the DIN rail — plan the rail fill accordingly. Installation depth of 55 mm fits standard distribution boards and sub-panels. The neutral conductor switching function is built in, so the neutral pole opens and closes with the phase pole.
Energy limiting class 3 means the breaker limits let-through energy during a fault — less stress on downstream components and wiring. The 5SQ design (design of the product) is Siemens' compact MCB platform for 50 Hz networks. AC/DC voltage type means it can also be applied in DC circuits up to the rated voltage, though the 3 kA breaking capacity should be verified against the DC fault current available.