What this MCCB does on the line
It's a line-protection device, not a motor-protection piece — the TM240 curve is sized for feeder and distribution duty, not for starting inrush. At 240 VAC it interrupts 220 kA, at 415 VAC 154 kA, at 440 VAC 121 kA, and at 500 VAC or 690 VAC it still holds 17 kA. The short-circuit current rating across the low-voltage band means this breaker clears hard faults without cascading upstream — useful when you're coordinating a panel downstream of a transformer or a main switch.
Thermal derating — the real ampacity
Rated 40 A at 40 °C, 45 °C, and 50 °C — no derating needed in a standard 40 °C panel. At 55 °C it drops to 39 A, at 65 °C to 38 A, and at 70 °C to 37 A. If your enclosure runs hot (poor ventilation, solar load, stacked breakers), size the load at 37 A, not 40. The TM240 release's adjustable li max goes up to 400 A, but that's the magnetic short-circuit pickup, not the continuous rating — don't confuse the two.
Width 76.2 mm (3 in), height 130 mm (5.12 in), depth 70 mm (2.76 in). The optional motor drive (Product Extension / Optional / Motor Drive = Yes) means you can add remote tripping or closing later without swapping the breaker.