The Siemens 3VA1225-5FF42-0BA0 is a SENTRON molded case circuit breaker rated for 125 A continuous and built for line protection. Four poles, TM240 thermal-magnetic overcurrent release, and an integrated undervoltage release — this is the variant you spec when the panel needs UVR trip on loss of control voltage and the load is a feeder or distribution bus, not a single motor.
Breaking capacity and selectivity
The interrupting ratings climb with the voltage drop: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, 30 kA at 500 V, and 17 kA at 690 V. That 187 kA figure at 240 V is the headline — it clears a high-fault bus without upstream cascading, which matters when you're coordinating a main-tie-main or a transformer secondary. The 690 V rating at 17 kA still covers most industrial distribution boards.
Thermal derating and power loss
Rated 250 A continuous at 40 °C, 45 °C, and 50 °C — no derating needed in that band. Above 55 °C it steps down: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, 223 A at 70 °C. The maximum power loss is 59.5 W, so panel ventilation matters if you're stacking breakers in a sealed enclosure. Operating range is -25 °C to 70 °C; storage from -40 °C to 80 °C.
Physical fit and mounting
Dimensions: 70 mm depth, 140 mm width, 158 mm height. Four-pole frame, so it occupies the full width of a standard MCCB mounting footprint. The 3VA series uses the same panel cutout and bus-bar spacing as earlier SENTRON frames, so it drops into an existing 3VA panel without re-drilling. No communication function on this variant — it's a standalone thermal-magnetic breaker with undervoltage release, no trip indicator.