Siemens Sentron
Siemens 3WL Repair & Refurbishment
Siemens 3WL (Sentron WL) air circuit breakers, frame sizes I to III, 630 to 6300 A, with ETU15B through ETU76B trip units — stripped, rebuilt and injection-tested. The breaker on our homepage is one.
- Frames3WL1 I · II · III
- Trip unitsETU15B – ETU76B
- Turnaround24–48 hrs once quoted
- Warranty12 months
The range
A well-built breaker with a few known weak points
The 3WL is a sound design. What wears is specific. The secondary connector — the block of pins at the top of a drawout unit that carries every control and trip signal — takes damage from repeated racking and from cabinet vibration, and an intermittent pin looks exactly like a random trip-unit fault. Auxiliary switch blocks go intermittent. Motor operators and the closing/opening solenoids reach the end of their life on high-operation duty. And on units past fifteen years the mechanism grease hardens, closing slows, and the breaker eventually refuses to latch.
We strip and rebuild the mechanism, replace motor operators, solenoids and auxiliary blocks, renew main and arcing contact sets, restore or replace the secondary connector and the wiring behind it, and test the ETU by secondary injection across every enabled element. Rating plugs, ETU upgrades (a 25B to a 45B for the LCD and ground-fault function, say) and communications modules are fitted and proven in the workshop.
| Secondary connector | Pin damage and intermittency from racking; the commonest cause of "random" faults |
| Motor operator & solenoids | End-of-life on high-operation duty; brushes and gear train on the motor |
| Mechanism | Hardened grease, slow or incomplete closing, latch wear |
| ETU trip units | Rating plug faults, display failure, drift; ETU15B/25B/27B/45B/76B all tested and replaced |
| Contacts | Main and arcing contact erosion; arc chute splitter wear |
| Auxiliary switches | Intermittent position and ready-to-close signals to the controller |
FAQs
Frequently asked
The ETU shows a fault but injection testing passes. What's wrong?
Look at the secondary connector and the wiring behind it before the trip unit. On a 3WL the connector is the weak point and an intermittent pin produces exactly this pattern. It is a repair, not a replacement.
Can you upgrade the ETU?
Yes. ETU15B or 25B to a 45B or 76B for ground-fault protection, metering and communications is a workshop job; the new unit is set to your protection settings and injection-tested at them.
Do you repair 3WL breakers from wind turbines and US sites?
Yes. 3WL units in turbine bases are a regular part of the work, and we air-freight 3WL breakers to and from US customers. See wind energy and repair for US operators.
Is a 3WL mechanism lock-up repairable?
A 3WL that has locked with the contacts closed — often during a contact change — is a strip-down job, not a scrap unit. The latch and the interlock linkage are freed, inspected and rebuilt, and the breaker is proved through its full operating sequence before it leaves.
Get started
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.
- Workshop & office01977 253063
- Out of hours07496 013884
- Email & photosinfo@circuitbreakerrepair.co.uk
- WorkshopUnit 13–17 Dale Court, Pontefract, West Yorkshire WF9 3FL