NETA Level III
There is a small retaining spring on the Magnum DS operating mechanism that can become worn and will break loose during a trip operation, causing a trip free condition on the next close operation. This one small spring is not held in by any retaining clips, and if it pops loose, you will never get the breaker closed again.
I discovered this while primary-injecting a 4000A double-wide main breaker that had this issue. After running through the first couple of long time tests, the breaker started tripping free. I removed the face from the breaker, and after some looking, noticed a spring on the right side of the operating mechanism hanging off its pin.
As you can see in the photo, the spring keeps tension on the trip latch which must be pulled up after a charging operation. Connect the spring from the main pin on the trip latch and bring it up to the small pin just behind the close button (Push On). It's a poor design by EATON, as there are no retaining clips holding the spring in place.
After putting the spring back where it belongs, the breaker closed but tripped free on the next test. I pulled the face off and found the spring hanging again! After comparing it to another from a spare breaker, it was obvious the spring was stretched out a bit and just didn’t have the tension necessary to stay in place.
Keep in mind this was a 4000A main breaker feeding a critical switchboard. Luckily this was all found during regular maintenance. Just think, if this breaker would have tripped during normal operation, the customer would have never gotten it closed and would have been on generator until repairs could have been made.
Ultimately I replaced the spring with one from a spare breaker and now the Main is working flawlessly. Isn't it amazing how one small part that probably cost less than $1 to manufacture could cause such a catastrophe? Hopefully this will help anyone in the field who runs into a Magnum DS that is tripping free.
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