What the D curve and 1.6 A rating mean for your panel
The 5SY4315-8 is a 3-pole miniature circuit breaker from Siemens' SENTRON family, designed for DIN-rail mounting in distribution boards and control panels. Its D tripping characteristic means it handles inrush currents 10–20× rated current before the magnetic trip operates — the right choice for motor circuits, transformers, or solenoid loads that draw a heavy start-up surge without nuisance tripping. At 1.6 A rated current (AC, per IEC 60898), this breaker protects branch circuits feeding small motors, contactor coils, or control transformers. The rated current derates with ambient temperature: 1.54 A at 40 °C, 1.5 A at 45 °C, 1.47 A at 50 °C, 1.44 A at 55 °C, and 1.4 A at 60 °C — if the panel runs hot, the actual continuous load must stay below the derated figure.
Breaking capacity — selectivity headroom in a fault
Rated breaking capacity is 10 kA per IEC 60898 and 35 kA per IEC 60947-2. The 35 kA figure under the industrial standard means this breaker can safely clear a fault up to that level in an industrial panel where the prospective short-circuit current is higher than a residential installation. For DC circuits (per IEC 60947-2), the breaking capacity is 15 kA. Overvoltage category III and pollution degree 3 suit it for fixed installations downstream of the main distribution board — the typical environment in a machine control cabinet or sub-distribution panel.
Physical fit and mounting details
Occupies 3 modular width units (54 mm total width) on a DIN rail. Depth is 76 mm, height 90 mm, installation depth 70 mm. The quick-assembly fastening method means it snaps onto the rail without tools and can be mounted in any position. IP20 protection (with connected conductors) is standard for indoor panel use. The combined terminal at both top and bottom accepts the supply cable from either end — no need to orient the breaker a specific way.