That 400 A holds flat through 50 °C — no derating needed until you push past 55 °C, where it steps down to 384 A at 55 °C, 372 A at 60 °C, 356 A at 65 °C, and 340 A at 70 °C. For a cement plant or kiln control room running hot, this means you can size the breaker at its full 400 A nameplate if your enclosure ambient stays under 50 °C; above that, you read the thermal curve directly off the spec. Breaking capacity is the headline number that decides fault coordination: 330 kA at 240 V, 242 kA at 415 V and 440 V, 187 kA at 500 V, and 13 kA at 690 V. That 330 kA at 240 V is high enough for most secondary-side transformer feeds or large motor control center mains; the 13 kA at 690 V still clears a solid fault on a 690 V line, but you'll want to verify the available fault current at that voltage before committing the BOM line.
ETU340 trip unit and N-conductor protection
The ETU340 is an electronic overcurrent release with adjustable N-conductor protection — configurable to OFF, 50 %, or 100 % of the phase current. That matters on a 4-pole breaker feeding a line with a neutral that may carry harmonic content or unbalanced return current; you set the N-pole protection level to match the load, not just leave it at a fixed ratio. The trip time is fixed at 1500 ms (tr min and tr max both read 1500), so this is not a short-time adjustable unit — it's sized for selective coordination where the downstream breakers clear faster, and this one waits for them.
Panel fit — dimensions and environment
Dimensions: 248 mm high, 184 mm wide, 110 mm deep.