The Siemens 5SL3640-6 is a SENTRON miniature circuit breaker rated 40 A at 400 V AC with a B tripping characteristic, switching 3 poles plus switched neutral (3P+N).
This breaker occupies 4 width units (72 mm) on a DIN rail, with a depth of 76 mm and an installation depth of 70 mm — no surprise for a 4-pole MCB; it fits standard distribution boards without a deep enclosure. The operating range spans -40 to 75 °C, with periodic exposure to +55 °C and 95% humidity allowed, which covers unheated utility rooms and outdoor-rated enclosures.
The B characteristic (3-5x In) means it holds through normal resistive load starts but trips fast on a dead short; don't use it on circuits with high inrush like large transformers or multiple motor starters without checking the trip curve. The neutral pole is switched (3P+N), so it disconnects the neutral as well as the phases — required in some regional wiring codes and useful for full isolation during maintenance.