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Re: NST current limit adjustment.



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

Hi All!

 If you know the voltage of your NST, it's going to be much safer (and
easier) to buy a cheap analog amp-clamp from radio shack or harbor freight
tools.  I think they have a $19 one.  You clamp it on a lead to the NST's
primary windings.

 Finding the output in mA is easy,

   120 * input amps gives you watts, divide watts by the NST's output
voltage,  like my 15/30 I depotted

  originally supposed to draw 3.75 A, actually around 3.8 or so.  Close
enough.

 I knocked out shunts, and it drew ~12A from the wall.

120 * 12 = 1440  / 15000 = .096


 So the 15kv NST is putting out ~96mA now that it's de-shunted.  To me, it's
much safer than playing with the HV side and taking any kind of risk of
cooking a DMM.  The real output current of the NST isn't an exact number,
nor does it need to be.   The above method gets you into the ballpark, and
is enough information for choosing tank cap values.

 You can use a DMM inline to measure current, but most can only handle 10A,
and the kickback from a running coil will cook it in nothing flat.   I don't
recommend it.  Plus an analog meter will bounce while the coil is running,
but it'll let you get an idea of the average input current.  Useful in a pig
system.

    My $.02

Shad

----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, July 24, 2001 2:36 PM
Subject: Re: NST current limit adjustment.


> Original poster: "Jake Draper by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<cybermecium2-at-home-dot-com>
>
> So you just hook up the meter directly to the output of the NST?
>     -Jake D.
>     <mailto:cybermecium2-at-home-dot-com>cybermecium2-at-home-dot-com
>     http://taradev.cjb-dot-net
>
> -------Original Message-------
>
> From: <mailto:tesla-at-pupman-dot-com>Tesla list
> Date: Tuesday, July 24, 2001 07:46:25 AM
> To: <mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
> Subject: Re: NST current limit adjustment.
>
> Original poster: "Gregory Hunter by way of Terry Fritz
<twftesla-at-qwest-dot-net>"
> <ghunter31014-at-yahoo-dot-com>
>
> You can measure the NST current with a regular analog
> or digital multimeter connected across the HV outputs
> & set on the amps function. I've done this many times.
> The meter will short the voltage down to nearly zero,
> and the meter can read the 30ma without harm. Make
> sure the DMM internal fuse is good. I had a blown DMM
> fuse one time and didn't know it. The fuse acted like
> a spark gap and my meter was fried! Also, use a cheap
> DMM just in case some thing goes wrong. Hook
> everything up, get yourself and your hands clear, plug
> in the NST from a safe distance away, and read your
> current measurement from the meter without touching
> anything. Unplug the NST. Make your shunt adjustments,
> repeat...
>
> Greg
>
> --- Tesla list <tesla-at-pupman-dot-com> wrote:
> > Original poster: "Rick W by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>"
> > <rickwilliams404-at-earthlink-dot-net>
> >
> > Hey all,
> >
> > I've depotted and reassembled my first NST. Replaced
> > the thick tar paper
> > wrapping with polypropylene .075" thick.
> > I noticed during dissassembly that some of the shunt
> > plates were out by half an
> > inch for current adjustment. I noted the position of
> > everything before
> > continuing the disaasembly.
> >
> > However, I don't believe everything can be within
> > calibration even after
> > reassembling everything exactly as it was.
> >
> > So my question is "how to readjust the current limit
> > shunt plates?".
> >
> > NST:
> > Franceformer 15K 30ma 450VA.
> >
> > Available equipment:
> > O-scope
> > Variac
> > Multimeter
> > Bunch of 50W resistors anywhere from .1 ohm to 50K
> > ohms.
> > A lot of assorted other parts.
> >
> > I have no high voltage probe though. If I need one I
> > can get one in about a
> > week.
> >
> > Thanks!!
> >
> > Rick Williams
> > Salt Lake City
> >
> >
> >
> >
> >
> >
> >
>
>
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