Three poles, no neutral switching — it's a straight 3P device for three-phase branch circuits in industrial control panels or distribution boards. Rated breaking capacity is 10 kA per EN 60898, and 5 kA per UL 1077 / CSA C22.2 No. 235. That UL/CSA supplemental-protector rating means it's accepted in North American industrial panels as branch-circuit protection, though not as a full UL 489 listed breaker.
The D characteristic governs the magnetic trip threshold: typically 10–20× In (400–800 A instantaneous), so it holds through motor starting without dropping the circuit. If your load is resistive (heaters, lighting), a C curve would suffice and give better selectivity downstream — but for drives, transformers, or high-inrush gear, D is the right call. At 40 A and 400 V AC three-phase, this breaker covers a motor load up to roughly 22 kW (assuming 0.85 PF and 0.9 efficiency). The 440 V rating for both single-phase and multi-phase operation gives headroom on a 400 V nominal system. DC rating maxes at 72 V — not for 125 V DC control buses. Temperature derating matters: the breaker is rated for ambient -40 to 75 °C, but the thermal-magnetic trip calibrates at 30 °C. Above 40 °C, the continuous current capability drops per the influence curve (95% RH at 55 °C, 55% at 70 °C, 35% at 75 °C). In a hot enclosure near a drive or transformer, derate or upsize the frame.
Sealable (can be locked in OFF position for lockout/tagout). Touch protection on the terminals means finger-safe to IPXXB when wired.