Breaking capacity and selectivity
The 3VA1112-5GE42-0AA0-ZD00: The 55 kA Icu at 415 V puts this in breaking capacity class M — the middle tier in the 3VA1 range, above standard (S) and below high-performance (H). For a 125 A frame, that's enough headroom for most industrial distribution panels with typical transformer impedances. The 4-pole construction means it switches the neutral as well as the three phases, which is required for TN-S or IT systems where the neutral is distributed and needs isolation during maintenance. The fixed Ii=10 x In short-circuit pickup (1250 A) gives a reasonable selectivity window against downstream 16–32 A MCBs; for tighter coordination with smaller branch breakers, you'd want the electronic trip version with adjustable Ii.
Trip unit and adjustment range
The TM220 thermal-magnetic trip uses a bimetal element for overload and a solenoid for short-circuit. Overload protection Ir is adjustable from 88 A to 125 A via a dial on the front — that's a 70–100% range of In. This lets you fine-tune the breaker to the actual cable or load rating without changing the frame. The magnetic short-circuit pickup is fixed at 10 x In, so it's not adjustable. For motor feeders or transformer primary protection where you need a higher Ii to avoid nuisance tripping on inrush, the ATFM variant offers a different curve; verify the coordination study before committing.