The Siemens SENTRON 3VA1225-4FF42-0CE0 is a 4-pole molded case circuit breaker rated 125 A continuous, designed for line protection in distribution panels. Its interrupting capacity hits 121 kA at 240 V AC — enough to handle high-fault scenarios downstream of a transformer without cascading upstream. The 4-pole construction covers three-phase plus neutral switching, common in North American and European panel builds where the neutral needs disconnection.
Breaking capacity and thermal derating
Breaking capacity drops with system voltage: 75.6 kA at 415 V, 52.5 kA at 440 V, 17 kA at 500 V, and 11.9 kA at 690 V — so verify the available fault current at your service voltage before committing the BOM line. Continuous current holds at 250 A up to 50 °C ambient, then derates linearly to 223 A at 70 °C. That 250 A frame rating means this breaker can be applied in a panel with ambient up to 50 °C without derating the main conductors.
Built-in undervoltage release
This variant ships with an undervoltage release (UVR) integrated — part of the auxiliary release design. If line voltage drops below the release threshold, the breaker trips, protecting downstream loads from brownout damage. No separate UVR module to wire in; it's factory-fitted. The auxiliary switch complement is 4 HQ switches, giving status feedback for remote monitoring or PLC inputs.