The C11B3TM040B is a Schneider Electric ComPacT NSXm 3-pole thermal-magnetic circuit breaker rated 40 A at 40 °C, with a 25 kA breaking capacity at 415 V AC. It's built to EN/IEC 60947-2, which covers the performance and testing requirements for low-voltage switchgear — so it's certified for distribution and isolation duty in commercial and industrial panels. The TM-D trip unit gives you fixed thermal and magnetic protection; no adjustments, no extra tuning at commissioning.
If your panel runs hotter — say 50 °C — you'll need to derate per the manufacturer's curve, which isn't on the nameplate but is in the product data sheet. That's enough for most secondary distribution panels fed by a transformer under 1 MVA. The 3-pole configuration suits 3-phase loads: lighting, small motor groups, or sub-distribution boards.
It's 9 module pitches wide (81 mm), 137 mm tall, 80 mm deep. The 35 mm pitch with spreaders (27 mm without) is standard for DIN-rail-compatible busbar systems. IP40 front-of-panel protection means it's splash-proof from the front but not sealed; keep it inside a cabinet.