The Siemens SENTRON 3VA1225-6EF42-0DH0 is a 4-pole molded case circuit breaker (MCCB) rated for line protection, with a continuous current Iu of 250 A and a TM240 thermal-magnetic overcurrent release. Its headline breaking capacity hits 220 kA at 240 V — that means it can safely interrupt fault currents up to that level without upstream cascading, critical for high-fault panels close to the transformer.
Breaking capacity across voltage levels
Breaking capacity drops as voltage rises: 154 kA at 415 V, 36 kA at 440 V, and 17 kA at 690 V. The 415 V figure covers most European industrial mains; the 690 V rating suits wind or marine distribution where higher line voltages are common. Rated insulation voltage is 800 V, so the breaker is designed for 690 V systems with margin.
Thermal derating and operating range
Rated continuous current holds at 250 A up to 50 °C ambient. Above that it derates: 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. If the panel ambient runs hot, size the load to the derated figure — the 70 °C limit matches the maximum operating temperature, so the breaker can sit in a sealed enclosure without losing its calibration.
Panel fit and auxiliary wiring
Footprint: 140 mm wide, 158 mm high, 70 mm deep. Fits standard SENTRON 3VA panel cutouts. The integrated auxiliary contact block is configured as 2 auxiliary switches plus 1 trip alarm switch (HQ version), and the unit includes an undervoltage release (UVR) — wired separately to a control voltage. If the control supply drops, the UVR trips the breaker, providing undervoltage protection for downstream loads.