What this MCCB is and what it does
The Siemens 3VA1125-6EE32-0AA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in distribution panels. It carries a 25 A continuous rating at 40 °C ambient, with a TM220 thermal-magnetic release that handles overload and short-circuit protection without external electronics. The 3-pole construction fits standard 3-phase feeders. Breaking capacity is the headline here: 220 kA at 240 V AC, 154 kA at 415 V, and still 121 kA at 440 V. That puts it in the high-interrupting category — useful for large transformer secondaries or bus-riser taps where fault current runs high. At 690 V it still holds 17 kA, so it can handle 600 V class systems as well.
Thermal derating and panel fit
The 25 A rating holds steady from 40 °C up to 50 °C, then drops to 24 A at 55 °C and 23 A at 65 °C. That's a gentle slope — you get full rating in most ventilated enclosures. The 70 mm depth and 76.2 mm width (3 inches) mean it fits standard Siemens 3VA panel footprints and bus-bar kits without adapters. Power loss is 8.5 W maximum at rated load — modest enough that internal cabinet heating from this one breaker is negligible, but worth summing if you pack a dozen in a small enclosure.