RE: Ballasting a Pole Pig

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>



> Original poster: Mddeming@xxxxxxx
>
>
> Who says paralleled transformers need to be identical?  Yes, the
output
> voltage ratings need to be (roughly) the same, and aesthetically, it'd
> be nice if they all looked the same, but there's no functional reason
> for them to be identical.
> Gary Lau
> MA, USA
>
> One way to check if they are "close enough" :
> With the transformers not connected to any load,  jumper
> corresponding hv terminals together with 100K 1/2W resistor on each
> side. Run the power up to full and if they don't smoke in say, 2
> minutes, then the transformers are "close enough for TC work". Repeat
> with each pair of transformers you are going to use.
> Matt D.
>

But consider a mismatch taken to the extreme - a functional NST in
parallel with a dead short circuit.  Since NST's are current limited,
it'll be happy to run into the short all day long, drawing only the
rated current.  While I've not tried it, I don't see damage occurring no
matter how large the voltage mismatch is, unless you parallel a 15kV
unit with a 6kV unit, and the resulting combination voltage exceeds the
lower voltage unit's insulation.

Regards, Gary Lau
MA, USA