400 A MCCB with ETU550 — selectivity and thermal derating
It carries a rated insulation voltage (Ui) of 800 V and delivers a breaking capacity of 187 kA at 240 V, 121 kA at 415/440 V, 75.6 kA at 500 V, and 17 kA at 690 V — figures that define its selectivity envelope in a distribution panel. The thermal derating curve is explicit: full 400 A up to 50 °C, then 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. This means the breaker can be applied at its nameplate rating in most ventilated enclosures, but a 55 °C internal ambient (common in crowded switchboards) forces a 6% headroom reduction. Maximum power loss is 96 W, which should be factored into enclosure thermal calculations. The ETU550 release supports communication functions, enabling integration with higher-level monitoring systems for trip data and load profiling.
Panel integration — dimensions and auxiliary wiring
The breaker measures 138 mm wide, 248 mm high, and 110 mm deep. The four auxiliary switches HQ are pre-configured — no separate auxiliary block to order — and their wiring should be planned for the control voltage present in the panel. No undervoltage release or shunt trip is fitted on this variant.