The Siemens 5SY4108-7KK11 is a 1-pole SENTRON miniature circuit breaker with C-curve tripping characteristic, rated 8 A. It carries a 10 kA breaking capacity per EN 60898 and a 20 kA rating per IEC 60947-2, giving it headroom for industrial panel coordination where the higher IEC standard applies. The design is specified for railway applications, which typically demands wider temperature tolerance and vibration resistance than commercial-grade gear.
At 8 A, this breaker protects a 1.8 kW resistive load on a 230 V single-phase line, or motor circuits up to about 1.1 kW (assuming 3x FLA inrush). The 10 kA SCCR under EN 60898 covers most commercial and light industrial fault levels; the 20 kA rating under IEC 60947-2 matches higher-capacity distribution panels where the upstream transformer can deliver a larger prospective short-circuit current. Temperature derating is published: at 40 °C ambient the breaker is rated 7.51 A, dropping to 6.43 A at 60 °C. The 18 mm width (1 modular unit) fits standard DIN-rail enclosures. Depth of 76 mm and height of 90 mm mean it clears most 100 mm deep enclosures.