Siemens 5SY7404-7 — 4-pole C-curve MCB for 400 V AC panels
It protects 400 V AC circuits in industrial control panels, mechanical engineering equipment, and distribution boards where the inrush of motor starters or transformer banks would nuisance-trip a B-curve device. The C-curve holds through 5–10× rated current before instantaneous trip, so it clears short-circuits without dropping loads during normal inductive starts. Breaking capacity is 15 kA per EN 60898 and 40 kA per IEC 60947-2, with a DC rating of 15 kA per IEC 60947-2. For UL 1077 / CSA C22.2 No. 235 installations the interrupting rating is 5 kA. That spread covers most panel SCCR requirements in Europe and North America — the 40 kA IEC figure gives headroom for high-fault utility feeds without cascading an upstream fuse.
Operating temperature range spans -40 °C to 75 °C, with humidity derating: max 95 % RH at 55 °C, 55 % at 70 °C, 35 % at 75 °C. Vibration resistance per IEC 60068-2-6: ±1 mm at 5–25 Hz, 50 m/s² at 25–150 Hz. The part carries the SENTRON brand designation and is classified per IEC 81346-2 and DIN EN 61346-2 as function F.