The Siemens 5SY4340-8CC11 is a 3-pole miniature circuit breaker from the SENTRON family, rated 40 A at AC with a D tripping characteristic and a 10 kA breaking capacity per EN 60898. It operates on 50/60 Hz supply and is designed for mechanical engineering and industrial panel applications, including railway equipment (the product designation flags railway suitability).
The 40 A rating holds at 35 °C ambient. Above that, the breaker derates: 37.6 A at 40 °C, 36.36 A at 45 °C, 35.04 A at 50 °C, 33.68 A at 55 °C, and 32.28 A at 60 °C. The breaker also accepts ambient humidity up to 95% at 55 °C, tapering to 35% at 75 °C.
Both top and bottom terminals accept combined (screw/clamp) conductors.
Halogen-free and silicon-free construction, sealable (tamper-evident seal provision). The design references EN 61346-2 and IEC 81346-2 function designation F (protective device). Suitable for railway applications per the product designation. No neutral conductor switching — this is a straight 3-pole overcurrent device.