Siemens 5SY4103-5 SENTRON MCB — 1-Pole, Characteristic A, High Breaking Capacity
The Siemens 5SY4103-5 is a 1-pole miniature circuit breaker from the SENTRON family, with a tripping characteristic of class A — the most sensitive standard curve, tripping at 2–3× rated current within 0.1 s. This makes it the correct choice for protecting semiconductor loads, control transformers, or long cable runs where standard B-curve breakers would allow too much energy through before tripping. Breaking capacity is rated at 10 kA per IEC 60898-1 and 35 kA per IEC 60947-2 at 400 V AC, with a DC rating of 15 kA at 60 V per IEC 60947-2 and 5 kA per UL 1077. The 35 kA IEC 60947-2 rating means this breaker can be used in high-fault-current industrial panels where standard 10 kA MCBs would need upstream current-limiting fuses or a larger frame. Rated operational voltage is 400 V AC single-phase, with a maximum of 440 V AC in single- or multi-phase operation. DC rated voltage is 60 V, maximum 72 V. Frequency range is 50/60 Hz.
Form Factor and Installation
The quick-assembly fastening system allows snap-on mounting in any position. Height is 90 mm. Combined terminals at both top and bottom simplify busbar and ring-tongue wiring. Neutral conductor switching is not provided — this is a 1-pole breaker for line-only protection.
Environmental and Derating
However, the breaker must be derated for humidity: maximum 95% relative humidity at 55 °C, 55% at 70 °C, and 35% at 75 °C. Vibration resistance per IEC 60068-2-6: ±1 mm at 5 to 25 Hz, 50 m/s² at 25 to 150 Hz. Halogen-free and silicon-free construction — important for environments where outgassing can contaminate sensitive contacts or optics (e.g., clean rooms, medical device manufacturing).
Designed and tested to IEC / EN 60898-1 (domestic and similar installations) and IEC / EN 60947-2 (industrial applications) / UL 1077 (supplementary protectors for North America). The dual rating means it can serve as a branch-circuit protective device in IEC panels and as a supplementary protector in UL panels — a distinction that matters when specifying for export or multi-standard facilities. Suitability for operation in mechanical engineering and industry per the manufacturer's designation. This is not a residential-grade MCB — it is built for the vibration, temperature swings, and fault-current levels found on factory floors.