Siemens Sentron WL · ETU
Siemens 3WL Repair and Refurbishment
The 3WL is a sound breaker with a few well-known weak points: the secondary connector, the motor operator, the solenoids and, past fifteen years, the mechanism grease. We rebuild all of them, test the ETU by secondary injection and return the breaker to its own cradle. Its successor's trip units won't fit it anyway.
- FramesSizes I, II, III
- Trip unitsETU15B–ETU76B
- Turnaround2–5 workshop days
- Warranty24 months on overhauls
Repair, don't replace
3WA is the successor. It doesn't drop in.
Siemens has moved on to the 3WA. Its trip units, the ETU600 and ETU800, are not interchangeable with the 3WL's ETU range, so a failed 3WL trip unit can't be swapped for a 3WA one. Replacing the breaker means a new frame and a different trip unit family, with new settings to prove.
Repair keeps the 3WL you have. Mechanisms are stripped and rebuilt, motor operators and solenoids are replaced, contacts are renewed, and the secondary connector and the wiring behind it are restored. The ETU is tested by secondary injection, and replaced or upgraded within the 3WL family if it needs to be. The breaker goes back into its own cradle with its own secondary wiring. No adapter, no controller re-commissioning, no board project.
For IEC-frame 3WL breakers on US sites, there is often no local repair route at all. That is why our 3WL case study came from a US wind farm.
Common faults
What fails on a 3WL
The weak points are specific, so diagnosis is usually quick.
Secondary connector
The pin block at the top of a drawout unit carries every control and trip signal. Repeated racking and cabinet vibration damage the pins, and an intermittent pin looks exactly like a random trip unit fault.
Motor operator and solenoids
Closing and opening solenoids and the motor operator wear out on high-operation duty. On the motor it is usually the brushes and gear train.
Mechanism
On units past fifteen years, the grease hardens, closing slows and the breaker eventually won't latch. Corrosion can seize it completely.
ETU trip units
Rating plug faults, display failures and drift across ETU15B, 25B, 27B, 45B and 76B.
Contacts and arc chutes
Main and arcing contact erosion, and wear on the arc chute splitter plates.
Auxiliary switches
Position and ready-to-close signals that go intermittent and confuse the controller.
The refurbishment
What a 3WL overhaul includes
- Complete strip-down: trip unit, secondary terminal blocks, mechanism, motor, arc chutes and poles off the frame, each part labeled
- Every mechanism part cleaned individually, not wiped over as an assembly
- Broken handles, cracked internal plastics and worn latches replaced
- Mechanism rebuilt and re-lubricated, then run through charge, close and open by hand and by motor
- Motor operator, solenoids and auxiliary switch blocks replaced as needed
- Main and arcing contacts renewed; arc chutes inspected
- Secondary connector and wiring restored or replaced
- ETU tested, replaced, or upgraded (for example a 25B to a 45B for the display and ground-fault function), with rating plugs and communication modules fitted and proven
How it is tested
Secondary injection on the ETU across every enabled element, contact resistance per pole, insulation resistance and mechanical operation, all recorded against the serial number.
Case study
A seized 2500 A 3WL from a US wind farm
The breaker arrived with its mechanism seized solid, rust through every link and pin, cracked internal plastics, a snapped charging handle and carbon tracked from pole L1 into the arc chute. It had an ETU45B trip unit.
We stripped it to the frame, cleaned every part, replaced the broken ones, rebuilt the mechanism and cleaned the L1 pole and arc chute. After injection testing on the ETU45B, it was air-freighted back four days after it arrived in the workshop.
Coverage
3WL models we repair
| Frames | 3WL1 frame sizes I, II and III, fixed and drawout |
| Ratings | 630 A to 6300 A |
| Trip units | ETU15B, ETU25B, ETU27B, ETU45B, ETU76B |
| Upgrades | ETU upgrades within the 3WL family, rating plugs, communication modules |
| Not interchangeable | 3WA trip units (ETU600, ETU800) do not fit a 3WL |
From your site and back
Turnaround, Express and exchange
Standard
About 3 days air freight each way and 2–5 working days in the workshop. Typically 8–11 working days door to door, plus customs clearance.
How it worksExpress
A 1–2 day workshop turnaround, about 7–8 working days door to door plus clearance.
Exchange units
We hold many tested units in the UK*. If yours is in stock, it flies out the day you report a fault.
Exchange unitsCustoms
DAP or DDP. We prepare the commercial invoice and the repair-and-return paperwork.
Shipping & customs*Subject to model and rating.
FAQ
Siemens 3WL questions
Can we fit a 3WA trip unit to our 3WL?
No. The 3WA's ETU600 and ETU800 trip units are not interchangeable with the 3WL. A failed 3WL trip unit is tested and repaired, or replaced within the 3WL ETU family.
The ETU shows a fault but injection testing passes. What's wrong?
Check the secondary connector and the wiring behind it first. On a 3WL the connector is the known weak point, and an intermittent pin produces exactly this pattern. It is a repair, not a replacement.
Can you upgrade the ETU?
Yes. For example an ETU15B or 25B to a 45B or 76B for ground-fault protection, metering and communications. The new unit is set to your settings and injection-tested at them.
Our 3WL has locked up with the contacts closed. Is it scrap?
Usually not. It is a strip-down job: the latch and interlock linkage are freed, inspected and rebuilt, and the breaker is proven through its full operating sequence before it ships.
Do you repair 3WL breakers from wind turbines?
Yes, regularly, including for US wind farms. Wind farms.
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.