Siemens circuit breaker 315 A,400 V

[hhhansen]

Hi
We have had some problems with damaged Siemens circuit breakers type 3VF5111-6EL71-0AS1, 315 A,400 V. 5 pcs. of these have been damaged and is an integrated part of motor starters. It seems like there is an internal short circuit in the circuit breader. Probably the short circuits have not been initiated by external components (cables, contactor,motor).

We believe there is a manufacuring problem, and want to know I any of you have experienced similar problems.

 

[dkle40h]

hi,
I would like a to ask for a little more information. Are you using the circuit breakers in a TN earthing system (solid earth) or an IT system, where the star point is earthed through a high impedance? Does the fault appear to be on a single phase?
Regards

 

[ScottyUK]

Hi hhhansen,

We have a number of Westinghouse breakers which are no longer available in the UK, but which have a stunning likeness to the Siemens parts. I think Siemens either bought the design or are re-badging the Westinghouse product. Allen Bradley also market the same design with their name (and pricetag ) on it.

We've replaced an number of Westinghouse breakers with the Siemens equivalents in the 3VF3, 3VF4, and 3VF5 frame sizes, and have had no major problems. The original Westinghouse items are showing the signs of age with expected levels of pole-face damage after clearing the occasional fault. Outright failures are considered rare among our installed base of several hundred devices. No issues at all with the Siemens parts which have been installed for a couple of years now.

Are your breakers correctly rated for fault current?

Which country are you in? Siemens Automation & Drives at Manchester in the UK have a very helpful technical department - a real pleasure to deal with. I haven't got a phone number other than an engineer's direct line, which I'm not prepared to post on here. It will be on their website.

 

[Broendum]

It is TN-S network and single phase faults!

Claus Broendum.

 

[jbartos]

Suggestion: The single phase fault can be 1.15 x three-phase fault. This is normally imbedded in ANSI built switchgear. The low voltage circuit breakers should have the 15% higher fault rating imbedded in their design and production.