Case study · air circuit breaker · US wind farm
A seized Siemens 3WL, rebuilt for a US wind farm
A 2500 A Siemens 3WL came to our workshop from a wind farm in the United States with its mechanism seized solid. Four days later it was on its way back across the Atlantic, rebuilt, injection-tested and certified, for a fraction of the cost of a new breaker.
- BreakerSiemens 3WL · 2500 A · ETU45B
- FaultSeized mechanism, corrosion, arc damage on L1
- Workshop time4 days, received to dispatched
- OutcomeBack in its own cradle, as new
Case file
Summary
| Problem | A drawout ACB out of service. The mechanism would not move by hand or by motor. The site is a US wind farm, with no local repair route for an IEC frame. |
| Breaker | Siemens 3WL air circuit breaker, 2500 A rating plug, ETU45B electronic trip unit. |
| Diagnosis | Corrosion through the operating mechanism, seizing every pivot. Broken internal plastics and a snapped charging handle. Carbon contamination through pole L1 up into the arc chute. |
| Repair | Stripped to the frame, every component cleaned individually, broken parts replaced, mechanism rebuilt and re-lubricated, L1 pole and arc chute cleaned and inspected. |
| Testing | Mechanical operation through the full charge, close and open sequence. Secondary injection on the ETU45B. Contact resistance and insulation resistance recorded. |
| Turnaround | 4 days in the workshop, from receipt to dispatch. |
| Logistics | Air freight from and back to the wind farm, with the export paperwork prepared by us. |
| Outcome | Returned in as-new condition and certified for service. A new 2500 A 3WL assembly runs £7,500–£12,000 before freight and fitting. |
As received
A mechanism that had stopped being a mechanism
When the crate was opened, the front cover was already off and the problem was plain to see. Rust coated every link, pin and latch in the operating mechanism. The pivots that let a 3WL close cleanly had seized. The charging handle was snapped off.
Several of the internal plastic moldings that locate the mechanism and carry the auxiliary switches were cracked or broken. On pole L1 there was carbon: the residue of arcing that had tracked from the contact area up into the arc chute.
The alternative on the table was a new breaker. For a fully configured 2500 A 3WL that is £7,500 to £12,000 or more in UK terms, plus the lead time and freight either way. Siemens has moved on to the 3WA, and 3WA trip units don't fit a 3WL. There was no local repair route for this IEC frame, so the breaker came to Yorkshire.
The work
Strip to the frame, clean every part, rebuild
Strip down
Trip unit, secondary terminal blocks, mechanism, charging motor, arc chutes and poles off the frame. Every part bagged and labeled by position.
Clean every part
Corrosion removed from each link, pin, spring and latch face on its own, not a wipe-over of the assembly, so the mechanism runs on clean bearing surfaces.
Replace and restore
Charging handle, cracked plastics and anything outside its wear limit replaced with new or serviceable parts. L1 cleaned from the contact area to the arc chute; contacts and chute plates inspected for erosion and tracking.
Rebuild and lubricate
Mechanism reassembled with the correct grade of lubricant and run through charge, close and open, by hand and by motor.
Test and return
Secondary injection on the ETU45B, contact resistance, insulation resistance, then crated and flown back with the certificate and strip-down report.
Outcome
Back in service as a breaker, not a compromise
The 3WL went back looking and operating like a new unit. The mechanism charges and closes cleanly, the L1 pole is clean, and the ETU45B has been proven by injection test, with a certificate to show it.
It went straight back into its own cradle with its own secondary wiring. No adapter, no change to the turbine controller, no switchboard project.
Against a replacement at £7,500 to £12,000 plus freight and fitting, the repair cost a fraction. Just as important for a US wind farm with no local IEC repair option, it was a route at all, and a four-day one.
What this means for your site
The same route is open to you
- All 3WL frame sizes, fixed and drawout, with ETU trip units
- Standard service about 8–11 working days door to door plus customs clearance; Express 1–2 days in the workshop
- Injection-test certificate, before and after photos and a parts list with every unit
- 24 months' warranty on full overhauls, 12 months on repairs
Send yours
Got a breaker in the same state?
Email the nameplate, a photo of the breaker and a description of the fault. We'll confirm we can do it and quote diagnosis and freight the same working day. You choose DAP or DDP, and we prepare the commercial invoice and repair-and-return paperwork.
Send us the nameplate
A photo of the nameplate and the fault is enough for a first answer. We reply the same working day with a recommendation and a price for diagnosis and freight.