The Siemens 5SY4603-8 is a SENTRON miniature circuit breaker with a D tripping characteristic, designed for 4-pole (3P+N) operation at 400 V AC. It carries a 10 kA breaking capacity per EN 60898 and 35 kA per IEC 60947-2, making it suitable for industrial panel protection where high inrush currents — typical of motor loads, transformers, or discharge lighting — demand a D-curve delay to avoid nuisance tripping.
The 10 kA rating per EN 60898 covers the majority of domestic and light commercial installations. The 35 kA per IEC 60947-2 is the figure that matters for industrial switchgear — it tells you this breaker can safely interrupt a fault current up to 35 kA at 400 V AC without welding contacts or venting plasma, which is essential for coordination with upstream transformers or high-capacity busbars. Under UL 1077 and CSA C22.2 No.235 the same unit is listed at 5 kA, so if your BOM specifies a North American code, confirm the available fault current stays within that limit. The DC rating of 15 kA per IEC 60947-2 at 60 V (max 72 V) covers battery banks or DC bus protection in the same enclosure.
Environmental and mounting details
Rated for ambient temperatures from -40 °C to 75 °C, with derating for humidity (95% 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) means it holds up on machine-mounted enclosures near rotating equipment.