The Siemens SENTRON 5SY7603-8 is a 4-pole (3P+N) miniature circuit breaker rated at 3 A with a D tripping characteristic, designed for 400 V AC systems. UL 1077 and CSA C22.2 No. 235 listing gives 5 kA at AC — important if the panel ships to North America. The 72 mm width (4 width units) means it occupies four 18 mm module spaces on the rail.
For BOM planning: the 5SY7603-8 is a fast mover in the 5SY7 line. If you're freezing a BOM for a new panel design, this part is stable and widely stocked. No PCN or successor has been issued — it's the current build.
Integration and compliance notes
The breaker is sealable (provision for a lockout tagout hasp) and touch-protected per the product feature listing. Temperature influence is specified: max 95% RH up to 55°C, derating to 55% at 70°C, and 35% at 75°C — relevant if the breaker sits near a heat source inside the enclosure. The position of the power supply cord is any, so line and load can land on either top or bottom terminals without restriction.
What the D-curve and ratings mean for your selection
The D tripping characteristic (10–20× In magnetic trip) is the key spec for motor and transformer branch circuits. At 3 A rated current, the magnetic trip fires between 30 A and 60 A — high enough to pass the inrush of a small motor or control transformer without nuisance tripping, but still fast enough to clear a hard short. For resistive or general-purpose loads, a C-curve (5–10× In) would be more common; the D-curve here is deliberately chosen for inductive kick. The 40 kA IEC 60947-2 rating is the industrial-grade figure — it matches the typical SCCR requirement for a 400 V distribution panel in Europe. The 15 kA EN 60898 rating is the domestic/commercial standard. If your panel label requires a 25 kA SCCR at 400 V, this breaker covers it under the IEC rating; the UL 5 kA figure is lower, so verify the UL label requirement if the panel is destined for North America.