The Siemens 3VA2612-5HN32-0AB0 is a 3-pole IEC frame 1250 molded case circuit breaker with a 55 kA breaking capacity at 415 V (class M). The ETU350 electronic trip unit provides LSI protection: long-time (overload, Ir adjustable 500–1250 A), short-time (short-circuit, Isd adjustable 1.5–10 × Ir), and instantaneous (Ii fixed at 10 × In). This gives you selective coordination downstream, so a fault on a branch trips the branch breaker, not this main.
What the ETU350 trip unit gives you
The ETU350 is an electronic trip unit with LSI curves — it covers overload (Ir), short-time (Isd), and instantaneous (Ii) protection. The Ir range from 500 A to 1250 A lets you match the breaker to the actual load without changing the frame. Short-time pickup from 1.5 to 10 × Ir enables zone-selective interlocking in a distribution cascade. The instantaneous pickup at 10 × In (12.5 kA) clears hard faults fast.
The two auxiliary switches are pre-wired to a terminal block; verify the changeover contact ratings match your control voltage (typically 24 VDC or 230 VAC). Allow adequate side clearance for arc-chamber venting and for the rotary handle mechanism if used.