Siemens 5SY6603-7 — 4-pole C-curve MCB for 400 V AC industrial panels
Rated 3 A at 35 °C and 400 V AC, it delivers 6 kA breaking capacity per EN 60898 and 30 kA per IEC 60947-2 — the higher figure governs fault-clearing in industrial panels where the upstream transformer can deliver substantial current.
Breaking capacity and selectivity — what the dual rating means
The 6 kA rating under EN 60898 is the domestic/residential standard; the 30 kA rating under IEC 60947-2 is the industrial standard that matters for panel coordination. Energy limitation class 3 means the let-through energy is low enough to protect downstream cables and equipment under fault conditions — relevant when coordinating with downstream sub-circuits or sensitive loads. Overvoltage category III confirms suitability for fixed-installation distribution boards, not just final circuits.
Thermal derating and environmental range
The 3 A rating is at 35 °C ambient. At 40 °C it derates to 2.86 A, at 45 °C to 2.78 A, at 50 °C to 2.71 A, and at 55 °C to 2.62 A. The operating range spans -40 °C to 75 °C, with humidity limits of 95% up to 55 °C, 55% up to 70 °C, and 35% at 75 °C.