The Siemens SENTRON 3VM1040-2ED32-0AA0 is a 3-pole molded case circuit breaker (MCCB) rated 40 A at 40 °C, built for line protection in distribution panels. Insulation voltage is rated 800 V, so it's comfortable on 480Y/277 V or 400 V systems with headroom. Breaking capacity varies by system voltage: 53 kA at 240 V AC, 32 kA at 415 V, 14 kA at 440 V, and 8 kA at 500 V. That 32 kA at 415 V is the number most panel builders will check first for common 400 V industrial feeds — it tells you this breaker can interrupt a bolted fault on a 400 A transformer secondary without upstream fuses needing to clear first.
The 40 A rating holds from 40 °C through 50 °C. At 55 °C it derates to 39 A, at 65 °C to 38 A, at 70 °C to 37 A. Power loss at rated load is 14 W — negligible for ventilation planning in a standard sheet-metal panel, but worth noting if you're packing six of these side by side. Dimensions are 76.2 mm wide (3 inches), 130 mm tall, 70 mm deep. That 3-inch width is the standard 3-pole MCCB footprint for this class — it occupies three 25 mm module positions on a DIN rail. IP40 on the front means tools and fingers are kept out, but it's not sealed against hose-down; keep it inside the enclosure.