What the ratings mean for panel fit
The 3VA1112-4GE42-0AA0: The 125 A frame carries full current without derating up to 50 °C — at 55 °C it's 122 A, at 60 °C 120 A, at 65 °C 117 A, and at 70 °C 114 A. If your enclosure runs hot, you lose only a few amps. The 121 kA at 240 V is the high-end interrupting capability; at 415 V it's still 75.6 kA, at 440 V 52.5 kA, and at 500 V or 690 V it holds at 11.9 kA. That's a lot of fault-clearing headroom for a 125 A frame — useful when the transformer is close to the panel. The TM220 release means thermal protection for overloads and magnetic (short-circuit) pickup at 10x In. No ground-fault monitoring built in — that's a separate accessory. The N-conductor protection is rated at 100%, so it's suitable for 4-wire systems where the neutral carries full phase current (e.g., high-harmonic loads).
Mounting and integration
Dimensions: 130 mm high, 101.6 mm wide, 70 mm deep. That 70 mm depth is shallow enough for most 200 mm deep enclosures with the door closed. Front IP40 — fine for a clean panel, not for washdown. The 4-pole footprint is wider than a 3-pole; check your DIN-rail or mounting-plate layout before swapping in. Power loss is 28.1 W max — factor that into your enclosure thermal budget.