It's built for industrial control panels and machinery where you need a high inrush tolerance — D-curve holds through motor-start and transformer-magnetizing surges that'd trip a B or C curve too early. Rated breaking capacity hits 30 kA at 400 V AC per IEC 60947-2, and 5 kA per UL 1077 and CSA C22.2 No. 235, so it covers both IEC and North American fault-current specs in one package.
Where it fits — panel and environment
Overall depth is 76 mm, so it clears a standard 80 mm deep enclosure backplate. Mount it in any position; the breaker doesn't care if it's vertical, horizontal, or upside down.
The D-curve trips magnetically between 10 and 20 times the rated current (40–80 A for this 4 A unit). That's what you want for motor feeders, solenoid banks, or transformer primaries where the inrush lasts a few cycles and a standard C-curve would nuisance-trip.
Sealable terminals allow the panel builder to lock the cover screws after commissioning, preventing unauthorized access to the live connections. Touch protection is built in per the product feature set.