Re: Single-bushing 14.7kV pigs. Thoughts?

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

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

Though I've only temporarily hooked up my pig to a coil once, it worked 
fine with only a single bushing.  The inside of the primary, the base of 
the secondary, and case of the transformer can all be grounded to your RF 
ground.  The other option, since you have two of them, is to run each of 
them off of 120 V (across the 240 V winding), and hook the outputs in 
series with the cases grounded together a la NSTs.  This will give you two 
HV output bushing, but it won't be floating WRT to ground as a true double 
bushing pig would be.  If you really want to go crazy, you could take the 
pig apart, and remove the wire from the HV side that is connected to the 
case, get another bushing and hook that up . . . but thats a lot of work in 
a big oily mess.  Or you could do what Dave Leddon did, and recase the pig 
in plastic: http://nick_tesla.home-dot-comcast-dot-net/TheVisiblePig.jpg

Sean


On Sun, 08 Feb 2004 08:50:28 -0700, Tesla list <tesla-at-pupman-dot-com> wrote:

>Original poster: "J. Aaron Holmes" <jaholmes-at-silicon-arcana-dot-com> After 
>months of searching and drooling over
>hopelessly-expensive 5kVA units on eBay, I finally
>found a cheap local source for used pigs (in Seattle).
>   The price was $100 for a 14,760V 15kVA unit, the
>smallest unit they had.  I was so ecstatic, I bought
>two for twice the price :)  Never hurts to have a
>spare, after all.
>
>Trouble is, they're the single-bushing sort.
>
>Now, this may or may not be a big deal; I've been a
>long-time lurker on this list, but I've never gotten a
>good feeling for exactly what the downside is to
>having only a single HV bushing.  If I wire up the
>outer two bushings on the LV side and ground the case,
>can't I just treat the case like the other HV bushing?
>
>Sounds like most people with single-bushing units have
>the 7200V variety, so series-phasing them makes sense
>for several reasons.  I'm not sure what good it does
>me, though.
>
>If this has been dealt with a million times, feel free
>to scorch me.  I deserve it :)
>
>Regards,
>Aaron
>