Re: [TCML] NST Measurements

[DC Cox <resonance@xxxxxxxxxxxx>]

Easiest way to solve this problem is call a manufacturer, ask for
engineering, and chat directly with an engineer.  He will give you the
correct answer without a lot of guessing.  He may also have valuable insight
into your measurement problems.  The engineers do this work all day long
and will give you valuable insight --- for free!

Dr. Resonance




On Tue, Jan 20, 2009 at 7:18 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:

> Hi Phil,
>
> I don't think so. I checked input voltages up to 17kV, and still it's way
> off. It's not the winding resistance, but the linearity of the voltage ratio
> that is not allowing the turns ratio to be identified. With a nice normal
> power transformer with good regulation characteristics, we could easily use
> the voltage ratio to compute the turns ratio as the losses are low. But I
> think with these NST's (or any shunted transformer), the extremely poor
> regulation due to the magnetic shunts affects the voltage ratio, and thus,
> the turns ratio is unknown. The question I think is how can we determine the
> turns ratio if the voltage ratio is so darn non-linear?
>
> I have no doubt that the shunt affects on inductance is the cause. How to
> get around it is not so easy to figure out.
>
> Bart
>
> FIFTYGUY@xxxxxxx wrote:
>
>> Folks-
>>      Any chance that the problem with loading the  secondary of an NST
>> with only 120V is the huge DC resistance of the secondary  windings? In the
>> transformer "model", that's a big series resistance that causes  a big
>> voltage drop. At 15,000 V no big deal, but at 120V pretty significant
>>  resistive losses.
>>    It's apparently common practice to add more turns  to a high-resistance
>> winding to account for the voltage drop. Often a cut-and  try approach to
>> transformer design. As D.C. Cox had pointed out to me years ago,  the turns
>> ratio is pretty far off from "ideal" in an NST.
>>  -Phil LaBudde
>> Center for the Advanced Study of Ballistic  Improbabilities
>>
>>
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