What this breaker is and what the ratings mean
The Siemens 3VA1112-4ED32-0AA0-ZD00 is a 3-pole IEC-frame-160 molded-case circuit breaker rated for line protection with a thermal-magnetic TM210 trip unit. The 36 kA breaking capacity at 415 V (class S) means it can safely interrupt a fault current up to that level without the arc flashing over or the breaker failing — critical for panel selectivity studies and SCCR compliance on 400 V distribution. In = 125 A is the continuous current rating; the overload protection Ir is fixed at 125 A (not adjustable), and the short-circuit protection Ii is fixed at 10 × In (1250 A). That fixed-trip design simplifies ordering — no trip-unit adjustment to mis-set in the field — but it also means the breaker is a straight swap for a 125 A line, not a general-purpose adjustable frame.
Where it lives in the panel
This breaker mounts in a standard IEC distribution panel or motor control center. The nut keeper kit included with this -ZD00 variant is a detail worth noting: it keeps the terminal nuts captive during wiring, which saves time on a production line or when an OEM in China is assembling DC Power cabinets. No loose hardware to drop into the panel.