Re: PTs

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Chris,

Tesla list wrote:

> Original poster: "Christopher Boden by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <chrisboden-at-hotmail-dot-com>
>
> I have several PT's 2 rated at 14.4kV at 1kVA with a 120 primary and a whole
> truckload of 2400VAC-120VAC 500VA (or are they 1K...hmmm Mark? you
> remember?) and I want to test them to see if they work.
>
> What should they read on an ohm meter?

Haven't got a clue... I would recommend a voltage test. It's just
transformer action, so use a volt meter
applying AC to the secondary terminals and measuring the primary "stepped
down" voltage which your meter can
handle. Seems to be a 120:1 ratio, so 120VAC on the secondary should show 1
volt on the primary.

> I got an MOT and clipped off the 2 wires for the filament then connected the
> sec lead around itself, still connected to the core.
> I connected the primary leads in series with the 14KV PT and got......squat.
> The voltage was discusting, I had to TOUCH the wires to get ANYTHING and I
> coulldn't draw ANY kind of an arc. It looked like getting about 100V at
> best.
>
> Why?

Probably too much inductive ballast but I haven't played with the MOT's in
my garage yet. Others can say
better than I.

> In the past I have connected an MOT directly to the wall as long as I didn't
> draw an arc, nothing happened. Pull an arc, couple seconds later, tip the
> breaker. Tried connecting the big PT straight to mains and 2 seconds after
> plugging it in, BEFORE I drew an arc, it tripped the breaker.
>
> POO!
>
> Why?

EEEEKKK!!! This was a lesson. You just found out why external ballast are
used on PT's and PIG's. These are
"not" internally ballasted transformers and will try to draw massive amps
when connected directly without
some type of resistance (or inductive ballast) in the circuit. These are
known as "externally ballasted
transformers" and are therefore seriously dangerous if you became the
ballast. Get a variac or a welder or
even a heater element (something) to ballast the current (hook in series as
you did with the MOT - a variable
ballast is nice to use obvisously to change and control the amount of
inductive ballasting - variacs,
welders, etc...).

Bart A.

>
> help, I'm confused (as usual)
>
> Christopher A. Boden Geek#1
> President / C.E.O. / Alpha Geek
> The Geek Group
> www.thegeekgroup-dot-org
> Because the Geek shall inherit the Earth!
>
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