Re: [TCML] Can i use an NST as ballast ?

[Bert Hickman <bert.hickman@xxxxxxxxxx>]

Hi Andreas,

Assuming that your new HV "plate" transformer has much less leakage 
inductance than your ballast NST(s), you can estimate the output current 
as follows:

Your NST:
Rnst = Turns Ratio of your NST = 8000/120 ~ 67
Inst = 60 mA (short circuit)
Ipri = Inst*Rnst = 67 * 0.060 = 4 Amps

Plate Transformer:
Rplt = Turns ratio of your plate transformer = 14300/120 ~ 119
Since the NST and plate transformer primaries are connected in series, 
they see the same current, so:

Isec (plate) = Ipri/Rplt = 34 mA (short circuit current from your 
NST-ballasted 14.3 kV transformer)

If you use more NST's connected in parallel in your ballast bank, 
compute the turns ratios and short circuit primary currents for each one 
and then add them all up for the total. You can use any mix of NST 
output voltages in your NST bank since each one will be short circuited. 
You'll need to figure the turns ratio for each NST and primary current 
separately when faceplate output voltages are different.

Bert
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Andreas wrote:
> Thanks,
>
> In a ballpark what current can i expect from the larger HV transformer
> if i hook up my NST to the primary for ballast ?
>
> --------------------------------------------------
> From: "Teslalabor" <teslalabor@xxxxxxxxxxx>
> Sent: Monday, October 25, 2010 6:43 PM
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Subject: Re: [TCML] Can i use an NST as ballast ?
>
> > Yes, you can use shorted NST's for current limiting. The more power
> > you need, the more shorted NSTs in parallel.
> >
> > ----- Original Message ----- From: "Andreas" <andreasho@xxxxxxxxxxx>
> > To: <tesla@xxxxxxxxxx>
> > Sent: Monday, October 25, 2010 5:42 PM
> > Subject: [TCML] Can i use an NST as ballast ?
> >
> >
> > > Hi,
> > >
> > > I got this HV transformer i want to try out but it needs some current
> > > limiting.
> > >
> > > Left in the picture.
> > >
> > > http://i1212.photobucket.com/albums/cc446/tesladude/trans1.jpg
> > >
> > > Specs:
> > >
> > > 55pounds
> > > 260vin
> > > 14.3Kvout
> > > 1200VA
> > >
> > > DCresistance:
> > > Primary: 0.2 ohm
> > > Secondary: 882 ohm
> > >
> > > The extra wirering is for cable sheilds and temp.
> > >
> > > Could my 8Kv 60ma NST work as an ballast and what would the current be?
> > > I probably need to know the inductances for that ?
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> > > Tesla@xxxxxxxxxx
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