The TM220 designation means the thermal trip is fixed at 125 A (the frame rating), while the magnetic short-circuit pickup is adjustable — a common choice for feeder protection where you want the thermal element sized to the cable but some flexibility on the instantaneous trip threshold. Breaking capacity is the headline here: 187 kA at 240 V AC, 121 kA at 415 V, 76 kA at 440 V, and 17 kA at both 500 V and 690 V. The part is rated for line protection (feeder duty), not motor protection — no separate overload relay class or ambient-compensated curve. If you need motor branch-circuit protection, you would pair this with a separate overload relay or look at the 3VA motor-protective versions with electronic releases.
Rated 125 A at 40 °C through 50 °C, then it derates: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, 114 A at 70 °C. In a sealed, uncooled enclosure at 60 °C ambient you lose 5 A — not a showstopper, but if the design load is 125 A continuous, you need to either ventilate the panel or uprate to the next frame. Four-pole width is about 4 inches.
Lifecycle stage is current — Siemens still builds this order code. No NRND flag or phase-out notice in the evidence.