400 A MCCB with ETU550 — line protection for main feeders
It carries a breaking capacity of 242 kA at 240 V, stepping down through 187 kA at 415 V and 440 V, 121 kA at 500 V, and 40 kA at 690 V — so it handles high-fault main feeders where the upstream transformer can deliver serious short-circuit energy. The thermal derating curve holds full 400 A up to 50 °C, then drops to 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C; if your panel ambient runs hot, size the breaker for the actual enclosure temperature, not the nameplate.
Dimensions are 248 mm height, 138 mm width, 110 mm depth — a standard SENTRON 3VA2 frame size. The 3-pole block fits a 138 mm wide slot in a distribution panel or motor control center bucket.
Trip unit and auxiliary functions
The ETU550 trip unit includes a voltage trigger function and communication capability, so it can report status or accept a remote trip signal on a digital network.