This is why 99% of all pole transformers have lightning/surge protectors on
the HV windings.
Best Regards
Dave Sharpe
On Wed, Jan 9, 2019 at 11:34 PM David Rieben <drieben@xxxxxxx> wrote:
> So sorry to hear that addressing the ‘obvious’ faulty spot on your
> transformer didn’t resolve your high current draw and failure of the high
> voltage output. I would say that the problem likely remains somewhere in
> the high voltage windings of your transformer. Unfortunately, I have
> personally never had much success fixing a transformer that failed in the
> manner that you describe the failure of yours. I was really hopeful that
> the small burn spot on the outer surface of your hv windings was the cause
> of your failure, but since addressing that issue failed to mitigate the
> issue, it is likely that the fault lies much deeper inside the windings!
> :-( This renders the feasibility of home shop repair a speculative venture,
> for sure!
>
> I may need to reconsider my ‘arczilla’ shenanigans for the health of my
> transformer.
>
> David
>
> Sent from my iPhone
>
> > On Jan 9, 2019, at 6:34 PM, Tyler LaVite <tlavite@xxxxxxxxx> wrote:
> >
> > Hello all! I wrote before talking about repairing my 25kva 14400/7620V.
> Quick rundown Incase you missed last email chain... it’s a new transformer
> had an issue at shipping which is how I ended up with it... it was running
> fine till I ran a .125mF 100kv pulse cap in series with a Jacobs ladder...
> it just stopped and kept drawing 50 amps. At full arc it was ballasted to
> about 80-90 amps. With no arc it pulled nothing until the damage now it
> sits there at 50 amps with no arc output. So I pulled the core and found a
> small burn spot on the outside HV winding I pulled the paper and found it
> was just a dot the size of a ball point pen. I fixed that easily... tested
> and still pulling 50 amps... I don’t know if this is the proper way but
> obviously there is two HV windings I checked resistance on both windings
> separately.
> >
> > Here is a link to 10 photos showing all of my measurements can anyone
> make any sense of these? Also is there any good testing I can do with an
> oscilloscope and a signal generator?
> >
> >
> > https://flic.kr/s/aHsmyTD8z8
> >
> >
> >
> > Sent from my iPad
> >
> >> On Jan 6, 2019, at 10:14 PM, Bert Hickman <bert@xxxxxxxxxxxxxxxxxxxxx>
> wrote:
> >>
> >> Hi Tyler,
> >>
> >> If you've removed the dent and substantially increased the clearance
> distance between the affected winding and the case, the mineral oil itself
> should provide sufficient insulation.
> >>
> >> However, it you'd like to provide additional insurance to make the fix
> bulletproof, you could slip in a curled piece of 1/16" - 3/32" thick
> flexible natural LDPE sheet against the metal case opposite the location of
> the fault. You can simply curl a 6" wide strip around the inside of your
> transformer case so that it snugly lines the interior of the metal case.
> LDPE is compatible with mineral oil over the long haul, so it should last
> for the lifetime of the transformer. Old time coilers will remember times
> when HV Tesla Coil capacitors were constructed using LDPE sheet under oil
> as the dielectric material.
> >>
> >> Something like the following material:
> >> https://www.usplastic.com/catalog/item.aspx?itemid=23655&catid=705
> >>
> >> Good luck,
> >>
> >> Bert
> >>
> >> Tyler LaVite wrote:
> >>> Does anyone know what type of tape that is used on a transformer core
> to hold the nonexistent paper on the core? The tape they use to tape the
> seams?
> >>> Sent from my iPhone
> >>>> On Jan 4, 2019, at 7:07 PM, David Speck <Dave@xxxxxxxxxxxxxxxx>
> wrote:
> >>>>
> >>>> Tyler,
> >>>>
> >>>> Good to hear that the fix looks to be relatively simple.
> >>>>
> >>>> I would think that you will have to re-center the core inside the
> tank. At the voltages involved, a few layers of varnish are not going to
> provide adequate insulation. Distance from the can and lots of oil are
> what you will need to prevent further breakdown.
> >>>>
> >>>> Dave
> >>>>
> >>>>> On 1/4/2019 7:54 PM, Tyler LaVite wrote:
> >>>>> Guess what guys! I pulled apart my transformer tonight and found a
> tiny burn mark on the outer wrap of HV side. I opened the paper it was
> right next to the end and there is one tiny little dot on one wrap of wire.
> What I found out happened was when this transformer got its bushing hit by
> a fork lift it shifted the core and it was sitting on the tank and it
> burned a small dot through the paper and was grounding onto the can. A good
> couple of coats of electrical varnish should fix it right up... man I’m so
> happy good end to a Friday!
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--
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA USA
Sharpe's Axiom of Murphy's Law
"Physics trumps opinion!"
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