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Seriesing CT trannies was - RE: pig in overdrive...



Original poster: "sundog by way of Terry Fritz <twftesla-at-uswest-dot-net>" <sundog-at-timeship-dot-net>

Hi all,

Mulled it over, kicked it around, and it still don't make a whole lot of
sense.  I'll drag out 2 12kv NST's as soon as my shoulder allows (20lb nst
hurts to lift, not supposed to be lifting heavy things with that arm).  I
wanna try this.  Please excuse the ascii art.  This is supposing a
freeze-frame at the peak of the AC cycle.

  Let's say a 12kv center-tapped tranny.  Core is grounded. Mkay.

     HV +6---||||          ||||--- -6 HV
           ==||||==[][][]==||||==
           ==||||==[][][]==||||==
           ==||||-=[][][]=-||||==
             sec1  +Pri-   sec2

Okeydokey, each secondary is throwing out 6kv, either + or - at this
instant, to give you 12kv total difference.  They're 180deg out of phase.

     HV +6---||||          ||||--- -6-6---||||          ||||---- HV +6
           ==||||==[][][]==||||==   ^   ==||||==[][][]==||||==
           ==||||==[][][]==||||==   |   ==||||==[][][]==||||==
           ==||||-=[][][]=-||||==  grnd ==||||-=[][][]=-||||==
             sec1  +Pri-   sec2           sec1  -Pri+   sec2

This is in parallel, except half the trannies are grounded.  there's (in a
perfect world) 0v between the like polarities.  Only a max of 6kv present.

                          actually 0, its grounded
                                    |
                                    V
     HV -6---||||          ||||--- +6- ---||||          ||||---- HV +6
           ==||||==[][][]==||||==   ^   ==||||==[][][]==||||==
           ==||||==[][][]==||||==   |   ==||||==[][][]==||||==
           ==||||-=[][][]=-||||==  grnd ==||||-=[][][]=-||||==
             sec1  -Pri+   sec2           sec1  -Pri+   sec2

Now the trannyies are in series,(switched primary leads on 1 tranny) with
half of each tranny shorted to ground.Each terminal is now 180 out of phase
with it's neighbor, giving us still only a max difference of 12kv between
the outermost terminals. (or any 2 terminals for that matter)
    I can't see how you can get more than 6kv out of the secondary of either
tranny without floating the core.  Shorting a secondary to ground basically
removes it from the circuit (it's doing no real work so I ignore it),
leaving me only 2 secondaries, each making only 6kv and either in phase (0v
to each other) or antiphase (12kv to each other), with the cores at ground
potential.  And given that my turns ratio hasn't changed, how do I get 12kv
on either of the non-shorted secondaries?

Not tryin' to be obtuse or nuthin' this just isn't makin' any sense.  I just
can't see how to get more than 6kv out of either side of either tranny
without over-volting it (the individual secondaries) or floating the core
(and having to change the orientation of 1 secondary per NST).  Hmm, maybe
my ignorance is showing?

									Shad