The Siemens 5SY4314-8CV is a 3-pole miniature circuit breaker (MCB) with a D tripping characteristic and a rated current of 0.3 A. Its headline rating is a 15 kA breaking capacity at 400 V AC — that is the maximum fault current it can safely interrupt without welding contacts or rupturing the enclosure, which is the figure that governs coordination with upstream protective devices in a distribution panel.
The D0.3 curve means this MCB is designed for loads with high inrush current relative to steady-state draw — typically small transformers, solenoid valves, or control-circuit power supplies where the magnetic trip must ride through the initial surge. The 3-pole configuration suits it for three-phase branch circuits in a DIN-rail distribution board, where the 15 kA SCCR at 400 V provides enough headroom for most industrial panel secondary distribution.