The Siemens 5SY4504-5 is a SENTRON miniature circuit breaker rated 4 A at 35 °C with a tripping characteristic A, meaning it trips on short-circuit at 2 to 3 times rated current — fast enough to protect semiconductor loads or long cable runs where standard B-curves would let too much energy through before opening.
Characteristic A is the key differentiator here. Most panel spares are B or C curve; this one opens faster on overload and short-circuit, which makes it the right choice for protecting sensitive electronics, control transformers, or semiconductor rectifiers where a B-curve's 3–5x In window would let a fault ride through long enough to damage downstream gear. The 4 A rating derates with ambient temperature — at 40 °C it's 3.76 A, at 50 °C it's 3.5 A, at 60 °C it's 3.22 A — so if the breaker lives in a warm cabinet, size up accordingly. The 2 MW (36 mm) width means it occupies two standard 18 mm DIN positions.
Mounts on DIN rail in any orientation.
Designed to IEC/EN 60898-1 and IEC/EN 60947-2, with UL1077 recognition. Halogen-free and silicon-free construction. Suitable for mechanical engineering and general industry per the manufacturer's classification. The EN 61346-2 and IEC 81346-2 function code is F (protective device).