What this MCCB carries — and what it means up-tower
The Siemens SENTRON 3VA2325-6HL32-0AE0 is a 3-pole molded case circuit breaker rated for 250 A continuous current (Iu) with an ETU320 electronic trip unit. It's configured for line protection — no undervoltage release, no ground-fault monitoring, no communication module. What makes it interesting for a wind turbine or industrial feeder is the interrupting capacity: 242 kA at 240 V, 187 kA at 415 V, and still 40 kA at 690 V. That kind of SCCR headroom means it survives a bolted fault on a 690 V turbine collector bus without cascading upstream — no up-tower swaps when a short clears cleanly.
Thermal derating — the real-world current
The 250 A rating holds flat from 40 °C through 50 °C ambient. At 55 °C it derates to 240 A, at 60 °C to 235 A, at 65 °C to 230 A, and at 70 °C to 225 A. If this breaker lives in a sealed NEMA 4X enclosure on a nacelle roof in July, that 70 °C derate to 225 A is the number to size against — not the 250 A nameplate. The ETU320 electronic trip gives you adjustable pickup and time curves, so coordination with downstream 3VA breakers is straightforward.
Panel fit and wiring
Dimensions: 248 mm high, 138 mm wide, 110 mm deep. That 138 mm width on a 3-pole frame means it occupies three adjacent 45 mm DIN-rail spaces — standard for a 250 A SENTRON. The ETU320 is self-powered from the line-side current; no control power needed for the trip unit. Maximum power loss is 37.5 W, so factor that into enclosure thermal calculations. Operating range: -25 °C to 70 °C; storage from -40 °C to 80 °C.