The Siemens 3VA1225-5FF42-0HA0 is a SENTRON molded case circuit breaker (MCCB) rated for 125 A continuous current, fixed at that value — no adjustable thermal or magnetic range on the TM240 release. It is a 4-pole unit designed for line protection, with a shunt trip (STL) auxiliary release for remote tripping. Breaking capacity is voltage-dependent: 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. The insulation voltage is rated at 800 V.
Thermal derating and power loss
The breaker carries its full 125 A rating up to 50 °C ambient. Above that, it derates linearly: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, and 223 A at 70 °C. Maximum power loss is 57 W at rated current — relevant for enclosure heat calculations in a densely packed panel.
Physical fit and integration
Dimensions are 140 mm wide, 158 mm high, and 70 mm deep. It mounts on a DIN rail or panel-mount base in a standard distribution board or motor control center. The shunt trip release (STL) allows integration with emergency-stop circuits or undervoltage protection schemes — no separate undervoltage release is fitted on this variant.