Ratings that matter for panel fit
Footprint: 76.2 mm wide (3 in), 130 mm tall (5.12 in), 70 mm deep (2.76 in). That's a standard 3-pole MCCB width for a 40 A frame — it occupies three 25 mm DIN spaces if you're mounting it on a rail, but verify the Siemens 3VA mounting base for your specific enclosure backplate. Thermal derating is flat from 40 °C to 50 °C at 40 A, then drops to 39 A at 55–60 °C, 38 A at 65 °C, and 37 A at 70 °C. In a sealed panel running hot, you lose 3 A off the nameplate — plan your load accordingly. Maximum power loss is 10.8 W, so it won't cook adjacent devices in a dense layout. Rated insulation voltage is 800 V, and the breaker's interrupting curve drops from 187 kA at 240 V to 75.6 kA at 440 V, then 17 kA at 500–690 V. That's typical for a 40 A frame — the arc extinction gets harder as voltage climbs. For a 480 V panel, you're working with 75.6 kA SCCR headroom.
The basic switch inside is order code 3VA11405EF320AA0 — that's the internal mechanism. If you're stocking spares, that sub-assembly is the replaceable core; the rest of the 3VA1140-5EF32-0HC0 is the complete breaker with shunt trip and aux switches factory-installed.