Ratings and what they mean for fit
The 3VA1225-4GF42-0KH0: The 250 A rating holds flat from 40 °C to 50 °C — no derating needed in a typical 40 °C panel ambient. At 55 °C it drops to 243 A, at 60 °C to 237 A, and at 70 °C to 223 A. If your enclosure runs hot, that derating curve is the one that decides whether this breaker holds the load without nuisance tripping. The 121 kA interrupting rating at 240 V is the headline number, but the real-world SCCR for a 480 V panel is 75.6 kA at 415 V, and at 690 V it's 11.9 kA. That tells you the breaker is sized for high-fault locations — main switchboards, transformer secondaries, or large motor control centers — not just branch circuits. Insulation voltage is rated 800 V, so the breaker is suitable for 690 V systems with margin. Power loss at full load is 57 W — that's heat that has to be vented in a sealed enclosure.
Auxiliaries and integration
This variant comes with 2 auxiliary switches plus a trip alarm switch (HQ), and a shunt trip release (STL) for remote tripping. No undervoltage release, no ground-fault monitoring, no communication module. The shunt trip lets a safety PLC or E-stop circuit kill power remotely — useful for emergency-off chains or interlocked machine feeds. Dimensions are 140 mm wide, 158 mm high, 70 mm deep — a standard 4-pole MCCB footprint for DIN-rail or panel-mount installation. The supplied basic switch is order code 3VA12254GF420AA0, which is the internal switching mechanism.