Re: pig in overdrive...

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 2/27/01 8:39:12 PM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

> Hi all,
>  
>   I'm sorely confused by this.  You said centertapped, which is implying 2
>  secondaries 180 degrees out of phase at half the total voltage (each leg of
>  a 12kv NST only puts out 6kv relative to the core(ground).  I can't see how
>  you'd series it for more voltage, unless you grounded 1 HV output and
>  floated the core (and case) at 14kv.  

Shad,

You just ground one HV terminal of each pig and connect the terminals
together.  Yes, you do have to phase the primaries correctly or you'll
get no output at all.  You're basically creating a giant NST basically,
except there's no current limiting.  Each pig becomes like one
winding of an NST.

>  Grounding 1 HV leg and floating the
>  core will essentially make 1 long secondary, but you'd probably have to
>  fiddle with the primary connections, as the 2 secondaries in each pig would
>  be out of phase still.  

I don't know what you mean by fiddle with the primaries.  You just
phase the primaries so the HV outputs are out of phase so you get double
the output voltage of a single pig.  You don't have to do anything
to the core.  The core does not need to be floating.

>  At that point you'd still have the same turn/turn
>  ratio as you did before (60:1), for 14kv, or essentially a single-ended
>  tranny.  Then you could run 2 back-to-back like MOTs.   

Yes, back-to-back is another way of describing what I'm talking
about.  The hook up is the same as for MOT's, yes. 

>  But you'll still
>  have thi problem of floating the core at HV, and I don't like the idea of 
my
>  240v line being that close to a 14kv core (vs a grounded core).

The core is no closer to 14kV than normally.  Many professional
coilers (DC Cox for example) prefer to ground one HV terminal of
their pigs anyway.  I don't see what you're saying about a floating
core vs. grounded core.  You don't change anything about the core,
when you use this method.  The core will not be at 14kV, you 
can still ground it if you want to.
>  
>   The insulation in a pig will probably do it, but I can't see how you'd not
>  have to fiddle with the primary connections.  Did I get this right (it 
seems
>  logical to me), or did I hit the nail on the side instead?

You just phase the primaries properly so you get double the voltage
output of a single pig.

John Freau


>  
>                                           Shad
>