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 Ted L in NZ
> The post below from Crow deserves a little comment
>
> 1) MOTS have a separate Primary winding so with the core grounded the
> voltage stress on the outer MOTs is secondary to core not Sec to Pri. I
> alway ground my cores but their are some more complex configurations which
> avoid this.

If you ground all the cores, the outer transformers will have a much higer
voltage from the secodary to the core. They are designed with one lead of
the secondary connected to the core anways, not many kV from the core to
secondary. If you float the cores, you reduce the stresses from core to
secondary. If you do float the cores, the stresses are distributed between
the primary and secondary windings, which have more insulating space than
just core to secondary.

> 2) The V stress reqd in a 6 MOT systems (3 per side) is greatest on the
last
> MOT's BUT is actually only about 4.4kvrms because the voltage continues to
> rise as the outer MOT secondary progesses AWAY from the core towards free
> space.

Unless you are powering the transformer with floating power supplies and
have the cores grounded to the same potential as I take it you are hinting
to do, you still have the problem mentioned above.

> 3) Oil baths are possible to make neatly and in a non messy manner with
> modern plastic containers or the use of 6" plumbing fittings. (MOTS slip
in
> perfectly if feet are cut off)  The price of this inconvienience is low
> compared to the rewards of heat reduction and insulation improvment

Playing with oil is messy no matter what you do with it. As for heat
reduction, I'm not aware that sealing transformers in PVC housings is the
best way to try to sink heat.

> 4) Because the MOT's are modular it is very possible to make portable
> designs as each MOT can be handled separately.

A single 10kVA transformer with no frills (taps, suge arrestors) is around
200 pounds. It's not really that hard to move around.

KEN