The Siemens 5SY4603-8CV is a miniature circuit breaker (MCB) with a D3 tripping characteristic, configured as 3-pole plus neutral (3P+N). Its interrupting capacity is rated at 15 kA Icu at 400 V AC.
What the Ratings Mean for Fit
The D3 curve means this breaker is designed for loads with high inrush currents — typically motor starters, transformers, or discharge lighting — where a B-curve or C-curve would nuisance-trip on startup. The 3-pole-plus-neutral configuration suits three-phase four-wire systems (e.g., TN-S or TN-C-S) where the neutral requires overcurrent protection. The 15 kA Icu at 400 V AC is the maximum fault current the breaker can interrupt once; for applications requiring multiple operations under fault, check the Ics (service breaking capacity) value, which is typically a percentage of Icu for this class.