The Siemens 5SY4303-6CC is a SENTRON miniature circuit breaker (MCB) with a B tripping characteristic, rated 3 A at 230/400 V AC, and a breaking capacity of 10 kA per EN 60898. The 3-pole design (3P) protects three-phase circuits in industrial control panels, mechanical engineering, and general industry applications.
At 35 °C the MCB carries its full 3 A rating. Above that, derate linearly: 2.82 A at 40 °C, 2.73 A at 45 °C, 2.63 A at 50 °C, and 2.53 A at 55 °C. If the panel ambient runs warm — say 50 °C inside the enclosure — the effective continuous current drops to 2.63 A, so the load must be sized accordingly. The maximum ambient is 75 °C, with humidity limits of 95% up to 55 °C, 55% up to 70 °C, and 35% at 75 °C.
The housing is 3 modular-width units (54 mm wide, 90 mm tall, 76 mm deep, 70 mm installation depth).