Case study · Air circuit breaker · US wind farm
Seized Siemens 3WL Rebuilt to New — for a US Wind Farm
A 2500 A Siemens 3WL arrived from a wind farm in the United States with its mechanism seized solid, corrosion through the linkages, broken internal plastics, a snapped charging handle and carbon from L1 up into the arc chute. Four days in the workshop later it went back across the Atlantic as a fully rebuilt, tested and certified breaker — for a fraction of the £7,500–£12,000 a replacement would have cost.
- BreakerSiemens 3WL · 2500 A · ETU45B
- FaultMechanism seized · corrosion · arc damage L1
- Turnaround4 days in the workshop
- OutcomeReturned as new · new unit £7.5–12k avoided
Case file
Summary
As received
A mechanism that had stopped being a mechanism
The breaker came out of its crate with the front cover off and the story on its face. Every link, pin and latch in the operating mechanism carried a coat of rust; the pivots that let a 3WL close in a clean thump were seized solid. The charging handle had snapped. Several of the internal plastic mouldings that locate the mechanism and carry the auxiliary switches were cracked or broken. And on pole L1 there was carbon — the residue of arcing that had tracked from the contact area up into the arc chute.
The customer's alternative was a new breaker. For a fully configured 2500 A 3WL that is £7,500 to £12,000 or more, plus a lead time and the transatlantic shipping either way. For an IEC frame on a US wind farm there is no local repair route, which is why the crate came to Yorkshire.
The work
Strip to the frame, clean every part, rebuild
Complete strip-down
Trip unit, secondary terminal blocks, mechanism, charging motor, arc chutes and pole assemblies all removed from the frame. Every component bagged and labelled against its position.
Every part cleaned individually
Corrosion removed from each link, pin, spring and latch face — not a wipe-over of the assembly, but each part on its own, so the rebuilt mechanism runs on clean bearing surfaces.
Broken parts replaced
Charging handle, the cracked internal plastics and any component that did not meet the wear limit on inspection replaced with new or serviceable parts.
L1 pole and arc chute
Carbon contamination cleaned back from the contact area through to the arc chute; contacts and chute plates inspected for erosion and tracking before reassembly.
Rebuild and re-lubricate
Mechanism reassembled and lubricated with the correct grade, then exercised through its full charge, close and open sequence by hand and by motor.
Test and certify
Secondary injection on the ETU45B across its protection elements, contact resistance per pole, insulation resistance, and mechanical operation — recorded on the certificate against the serial number.
Crate and return
Four days after it arrived, back to the wind farm by air freight with the certificate and the strip-down report.
Outcome
Back in service as a breaker, not a compromise
The 3WL went back to the customer looking and operating like a new unit: a mechanism that charges and closes cleanly, a clean L1 pole, an ETU45B proved by injection test, and a certificate that says so. It dropped back into its own cradle with its own secondary wiring — no adapter, no re-commissioning of the controller, no board project.
Against a replacement at £7,500 to £12,000 plus freight and fitting, the repair was a fraction of the cost. Just as important for a US wind farm with no local IEC repair route: it was a route at all, and a four-day one.
Siemens 3WL repair · Wind turbine breaker repair · Repair for US operators
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Tell us about the breaker
Make, model and rating from the nameplate, plus a description of the fault. We'll come back with a clear recommendation and a fixed price — usually the same working day.
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- WorkshopUnit 13–17 Dale Court, Pontefract, West Yorkshire WF9 3FL