What it is and what it does
The Siemens SENTRON 3VA1125-6EF32-0AD0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection. It carries a continuous current of 25 A at 40 °C ambient and is fitted with a TM240 thermal-magnetic overcurrent release — the thermal element handles overloads, the magnetic element clears short-circuits. The 220 kA interrupting rating at 240 V means this breaker can safely quench a fault current up to that level without rupturing or welding contacts, which is essential for high-fault-capacity installations like transformer secondaries or large motor control centers.
Breaking capacity across voltages
Interrupting capacity drops as system voltage rises: 154 kA at 415 V, 121 kA at 440 V, and 17 kA at both 500 V and 690 V. At 690 V the 17 kA rating still covers most industrial distribution faults, but verify against the available fault current at the point of installation. The insulation voltage is rated 800 V, so the breaker is physically built for 690 V systems.
Thermal derating and panel fit
Current rating holds at 25 A from 40 °C through 50 °C, then steps down to 24 A at 55–60 °C and 23 A at 65–70 °C. If the breaker sits in a warm enclosure or next to other heat sources, use the 23 A figure for sizing. The 70 mm depth and 76.2 mm width (3-inch standard) fit a typical MCCB slot on a DIN rail or panel-mount base; the 130 mm height leaves room for auxiliary switch wiring above. Maximum power loss is 8.5 W — negligible for enclosure thermal calculations but worth noting in sealed cabinets.