What the ratings mean for fit
The 3VA1225-5FF42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated 250 A continuous at 40 °C — that is the current it carries without tripping in a 40 °C ambient panel. The TM240 thermal-magnetic fixed release means the thermal element is calibrated for 250 A; the magnetic short-circuit pickup is fixed at the factory. Four poles let it switch a three-phase plus neutral line, with the neutral protected at 50 % of the phase rating — standard for TN and TT systems where the neutral is not fully loaded. Breaking capacity is the headline spec: 187 kA at 240 V AC, 121 kA at 415 V AC, 75.6 kA at 440 V AC, 30 kA at 500 V AC, and 17 kA at 690 V AC. At 240 V this breaker handles the highest fault currents found on large transformer secondaries or industrial services. At 415 V the 121 kA rating covers most European low-voltage distribution where the prospective short-circuit current at the main panel can exceed 100 kA. The 17 kA at 690 V is relevant for 690 V drives or mining gear — few MCCBs hold that rating.
Derating and duty profile
The 250 A rating holds flat from 40 °C to 50 °C. Above that it derates: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, and 223 A at 70 °C. If your panel ambient runs 60 °C, the breaker effectively becomes a 237 A device — factor that into the load schedule. The TM240 release does not have adjustable thermal or magnetic settings; if you need a different trip curve, swap the breaker. Maximum power loss is 57 W — heatsink that into the enclosure volume.
Panel integration
The breaker measures 140 mm wide × 158 mm high × 70 mm deep — a compact four-pole footprint for a 250 A MCCB. It mounts on a DIN rail or can be screw-fixed to a backplate. Front IP40 protects against tool entry; the enclosure must be rated for the overall panel IP class. An optional motor drive (listed as a product extension) allows remote closing — useful for emergency-stop reset or automated transfer schemes.