What this MCB is and what the rating means
The Siemens 5SY4615-7CV is a 3-pole-plus-neutral miniature circuit breaker with a C-trip characteristic rated at 1.6 A. Its 15 kA breaking capacity at 400 V AC (Icu per IEC 60898) means it can safely interrupt a fault current up to that level without welding its contacts or cascading failure upstream — critical for downstream coordination in a distribution board where the fault current at the panel is high. The C-curve (5–10× In) is sized for moderate inrush loads like small motors or transformers; for purely resistive or lighting circuits a B-curve would trip faster on short-circuit.