This is the breaker you spec into a main feeder or heavy branch circuit where you need a single interrupting device that can handle the full load and clear faults fast. The TM210 overcurrent release means it uses a thermal-magnetic trip — thermal for overloads, magnetic for short-circuits — no electronic adjustments, no communication module, just a straightforward, field-reliable trip curve. The IP40 front protection keeps tools and fingers out of the live terminals but isn't rated for washdown — this lives inside a dry enclosure.
At 240 V, the interrupting rating is 121 kA. That drops to 76 kA at 415 V, 40 kA at 440 V, and 12 kA at 500 V. The 12 kA at 500 V is the limiting case; don't put this on a 500 V bus with more than 12 kA available unless you've got a current-limiting upstream device.
Thermal Derating — Don't Ignore the Cabinet Temperature
At 55 °C it's 39 A, at 60 °C it's 39 A, at 65 °C it's 38 A, and at 70 °C it's 37 A. If your panel ambient runs 65 °C (tight enclosure, solar load, next to a furnace line), you lose 3 A from the nameplate. That's a 7.5% reduction — enough to nuisance-trip if you sized the load right at 40 A. Always size the breaker for the actual cabinet temperature, not the 40 °C rating.
Depth is 70 mm, width is 76.2 mm, height is 130 mm. That's a compact footprint for a 400 A frame — it fits standard distribution panel gutters without crowding the bend radius on incoming cables. The 3-pole block takes up about 3 inches of rail space.