Re: Overvolting pigs?

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

Original poster: "Sean Taylor" <sstaylor-at-uiuc.edu> 

It's not a question of how long would the pig withstand the overvoltage,
but if you could even get it to that voltage.  I think I remember someone
saying that they ran a pig to 300 v in and it started saturating (too high
of a magnetic flux density in the core).  All that will happen if you put
240 V into the 120 taps is you'll get excessive current draw and heating
of the core.

The same goes for running the RSG from the NST: it would saturate from the
28.8 kV on the secondary.  NSTs are made fairly inexpensively, they aren't
even designed to withstand the full rated voltage forever, as when they
are loaded with a tube, the voltage is supposed to be around 1/2 of the OC
output.  Another problem with the NST is the internal current limiting -
the load of an RSG would certainly drop the voltage on the primary from
120 rather quickly, and phase control would be a real problem, as the load
changes, the phase changes.  I was thinking about doing a PLL type
controller for a RSG using the primary cap's voltage as a reference
waveform so that the RSG phase would stay sync'd with the primary voltage
no matter what the input, though that's still a long ways off.

Sean Taylor
Urbana, IL

On Tue, 13 Jul 2004 22:04:18 -0600, Tesla list <tesla-at-pupman-dot-com> wrote:

>Original poster: FIFTYGUY-at-aol-dot-com Folks-
>
>      After recent posts on running small low voltage x-formers
>backwards, and
>trying to power a 480V pig with 240V:
>      How much over the nominal voltage ratings will a typical pig
>withstand?
>I.e., if I put 240V into 120V taps how long will it put out twice the
>high
>voltage rating?
>      Seems a lot of folks variac the 14.4kV units to about 18kV out - any
>guesses how long it would withstand 28.8kV out?
>      While we're at it:
>      What, if anything, should be hooked up to the neutral tap of the LV
>side
>of the pig? Any theories as to balancing, filtering, etc., or is it
>better
>left unconnected? I feel the fewer house wires headed to HV land the
>better.
>      And speaking of running x-formers backwards and house wiring
>isolation, I
>was thinking of using a NST run backwards to provide 120VAC for the SRSG
>from
>the HV pig output to the primary circuit. So I suppose I should ask how
>long
>a 15kV NST will last with 28.8kV into the secondary...
>
>-Phil LaBudde
>