The Siemens 5SY4603-7CV is a miniature circuit breaker (MCB) rated for a short-circuit breaking capacity Icu of 15 kA at 400 V AC, in a 3-pole plus neutral (3P+N) configuration with a C-curve trip characteristic and a 3 A rated current. That 15 kA Icu at 400 V means it can safely interrupt a fault current up to that level without welding its contacts or cascading failure upstream — a key figure for panel builders coordinating selectivity in a 400 V distribution board. The C-curve (trips between 5 and 10 times In) suits it for general-purpose loads like lighting, small motors, and control transformers where moderate inrush is expected.
Snap-on mounting to DIN rail EN 60715 — standard 35 mm rail. The 3P+N form factor occupies four modular widths (4 x 18 mm) in the enclosure. For a panel OEM, that's a known fill factor; no surprises on the gland plate layout.