Re: shunts/Magnetek NST

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

Original poster: "harvey norris by way of Terry Fritz <twftesla-at-uswest-dot-net>" <harvich-at-yahoo-dot-com>


--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "cougercat by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <felix1063-at-home-dot-com>
> 
> Hello Group,
>  
> Does anybody have a photo of the transformer
> "shunts" that can be removed for
> greater power?
>  
> Thanks
>  
> --jeff
Yes I would like to see those also. My basic question
for the list is this, do ALL NST's have these shunts?
Recently I tried to measure the inductance of the
secondary of my 15,000 volt,30 ma Magnetek Jefferson
NST's with a Wavetek LCR meter. The Highest inductance
reading scale is 200 Henry, and it shows a overrated
value on the highest scale reading, meaning the
inductance is too high for the meter to measure. It
does however make a reading of 20,000 ohms on the
resistive reading.
    Discouraged I decided to calculate the value of
inductance by finding the impedance that the secondary
will have at 60 hz and delivering its rated 30 ma as a
shorted secondary. At 15,000 volts and delivering the
30 ma across the short, the acting impedance of that
secondary would be by Ohms Law extended to AC where
V=IR then becomes V= IZ :  15000(v)=.03(A)*Z where Z
then =15,000/.03= 500,000 ohms. Using the equation
Z(impedance)=sq rt [X(L)^2 +R^2]= 500,000=sq rt
[X(L)^2+ (20,000)^2] where then squaring both sides
yeilds
2.5 *10^11= X(L)^2+ 4*10^8 showing that X(L)^2 
=2.496*10^11 and therefore the sq rt of that value at
~499,600 ohms as the inductive reactance figure X(L)
Since X(L)= 6.28 Freq(L), we can then divide the
499,600 by 6.28(60) to obtaing the L value as ~1326
Henry.

So by the above calculations we can see that the 1326
henry secondary with 20,000 ohms resistance will
permit a current of only ~ 30 ma if short circuited.
This rated current that is delivered is already
current limited by the acting impedance of that
secondary. This is why I cannot understand what, why,
and where the shunt exists. I conclude at this point
in time that my Jefferson contains no shunts, and as I
have said it is already current limited by the acting
impedance of the secondary, based on the 20,000 ohms
figure that has been measured.

Terry had also posted figures for other NST's where
the resistance of this NST secondary had the highest
figure at 20,000 ohms. Is it possible that only the
jeffersons function this way without the need for a
shunt? Any comments on this shunt business, and
potential errors in my calculations showing that no
shunt exists on this transformer would certainly bring
me to a better understanding of this matter. Perhaps I
have made a silly error, and can stand to be
corrected.

Sincerely HDN

 


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