The 4-pole (3P+N) design covers three-phase circuits with a switched neutral, common in European distribution boards.
Derating and ambient temperature — the real-world current limit
The 40 A rating holds at 35 °C. At 40 °C it derates to 38.12 A, at 45 °C to 37.12 A, at 50 °C to 36.12 A, and at 55 °C to 35.08 A. If the panel runs warm — say 50 °C inside the enclosure — the breaker's effective continuous current is 36 A, not 40. The surrounding temperature influence curve also caps humidity: 95 % RH up to 55 °C, then 55 % RH up to 70 °C, then 35 % RH up to 75 °C.
Panel fit — DIN-rail footprint and mounting
Width is 72 mm (4 modular units), depth 76 mm, height 90 mm. Fastening method is snap-on, any mounting position.
Comparison with 5SY7210-7CC — same footprint, different rating
The 5SY7210-7CC is a physically identical 4-pole SENTRON MCB but rated at a lower current (10 A vs 40 A) with the same C curve and breaking capacity. The choice is purely the load current: 40 A for feeder circuits or larger loads, 10 A for branch protection. No footprint or coordination change needed.