The breaker's interrupting capacity reaches 121 kA at 240 V and 75.6 kA at 415 V, which gives you headroom for high-fault installations like substation feeders or large motor control centers.
Current derating — what the thermal curve means for your panel
The 125 A rating holds flat from 40 °C through 50 °C, then begins a gradual decline: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. The 28.1 W maximum power loss also contributes to internal heat rise, so factor that into your thermal budget.
This breaker delivers 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at both 500 V and 690 V. The steep drop above 500 V is typical for MCCBs with this frame size — the arc extinction physics limit the interruption at higher line voltages.
Built-in auxiliary components
The auxiliary switches give you remote status feedback — open/closed indication to a PLC or status lamp.
Physical fit — panel integration note
Dimensions: 130 mm height, 76.2 mm width (3 in), 70 mm depth. The 3-pole width is standard for a 125 A frame — it fits a 3-module DIN-rail slot or a bolted panel-mount footprint.