Re: Pole Pig Construction

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Crow Leader by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla-at-lists.symmetric-dot-net>

> Original poster: "tesla by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<tesla-at-paradise-dot-net.nz>
>
> Hi Ken
> Most intertesting points you make re floating the cores of MOT's in
stacked
> operation.
> Some observations on your comments
>
> 1) Yes it will distribute the stress between elements as you say.
> 2) Is this a good idea ? I have my doubts here. The primary is not made to
> accept this stress whereas the secondary is particularly near the outer
part

There is still physical spacing between the primary and core which can
probably take a few kV. If you get oil in that space you're even better off.

> which must hold back 2.2kv or so.
> 3) I think in all likelyhood MOT's are tough enough for either
> configuration.
> 4) There is an element of safety I think in gnd the core operation. It is
> not possible for secondary voltages to reach back to the mains I/P with
the
> associated risks of that event. It also places a barrier between the mains
> and any secondary strikes.

Any higher voltage short would be at worst across the primary winding, which
is not really a big deal as it just shorts the secondary. You are not going
to get many kV backing up into the power mains.

> 5) As you say simple series operation MUST introduce core to secondary
> stress. The distribution of this stress can be managed by adopting various
> configurations BUT it works OK in practice. MOT coilers report success
> regularly. I don't know what the limit is but 4 per side in oil is
reported
> without failures.

somebody did post a message today about a transfomer failing.

> 6) I do not have heat problems in my MOT's BUT I am sure that submersion
in
> oil will assist in heat removal. The thermal contact and conduction of oil
> is >> than air.

This may be true until you start to seal the assembly in a plastic box or
pipe.

> Some posters have said it is essential even for the unmodified MOT's in
the
> centre for this reason. I guess it all depends on the amount of ballasting
> and length of run times. I use modest ballasting to keep from overloading
my
> MOT's.
>
> 7) The impact of oil use may just be a personal thing. Don't Pigs have oil
> in them too. It can be managed easily with good construction. For me it
has
> been a set it (and yes putting the oil in was a little messy) and forget
it
> thing.

There is nothing to even set to have to forget about with a polemount
transformer. You don't need to ever touch the oil. The only way to get a
mess is to open it, or tip it over and pull the pressure relief valve.

> 8) MOT use is commented  by me in  to help those looking for cheap and
easy
> to get bits. I'm not trying to dismiss the pig at all I just respond to
MOT
> "put downs" which I feel are unbalanced . Many potential users rely on the
> "flavour" they get from postings. Most can't afford or are not equipped to
> use PIG's and I try to offer balancing thoughts and offer tips for those
who

Hmm. this may be the problem. I replied to the first posting with the stance
that trying to simulate or fake a polemount transformer may be just be an
overkill of effort and the problems I'd be worried about when connecting 7
or 8 modified transformers into some chain. On lower voltage use with a few
number of transformers it may make perfect sense.

KEN