What it is and what it does
The Siemens 3VA1125-3EF32-0KH0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection — meaning it guards the feeder, not a specific motor or load. Rated 25 A continuous at 40 °C with a 3-pole construction, it fits standard panel-mount cutouts and carries a 75.6 kA interrupting capacity at 240 V, which drops to 52.5 kA at 415 V and 32 kA at 440 V. That's enough SCCR headroom for most industrial distribution boards without needing a current-limiting fuse upstream.
Ratings that matter for fit
The 25 A rating holds flat from 40 °C to 50 °C, then derates to 24 A at 55 °C and 23 A at 70 °C — so if your panel ambient runs hot, you lose about 2 A off the top. The 800 V rated insulation voltage means it's comfortable on 480 V or 600 V systems without derating the dielectric. Physical footprint is 130 mm tall, 76.2 mm wide, and 70 mm deep — a compact 3-pole MCCB that fits the same DIN-rail or screw-mount pattern as other SENTRON 3VA frames.
Panel integration notes
Mounts in a standard panel cutout or on DIN rail via the optional adapter. The 3-pole block leaves room for auxiliary switches (2 aux + 1 trip alarm, per) and a shunt trip release — both field-installable without removing the breaker from the bus. Power loss is 8.5 W maximum, so ventilation in a sealed enclosure is advisable if you're grouping several breakers.