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Re: [TCML] Depot NST Measurements

Hi Phil,
When the HV side of the secondary is shorted (short circuit current), there is no voltage because it's shorted out. Measuring the short circuit current is simple. Set your digital meter to read about a 200mA scale. With the meter set to measure current (and leads in the correct socket), connect each lead across the HV output terminals. Then apply input power. That's all there is to it.
However, there are precautions. NEVER disconnect or connect the meter leads with power applied. This will give you a little shock and also kill your meter. As long as the output is shorted, there is no voltage across the output terminals. But as soon as you disconnect it, then the full voltage is felt and will immediately arc to the lead you disconnected.
Just make sure the meter is set and connected before applying power. And turn power off before connecting. I know all that appears common sense, but when making these type of measurements, it's easy to get out of step and make a mistake. 

Take care,
Bart

Phillip Slawinski wrote:

Interesting,

I have two questions.  First did you bother to measure short circuit
voltage?  Second what did you use to measure secondary current?

On Sun, Jun 29, 2008 at 4:44 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:


Hi All,

For someone not to long ago I mentioned I would remeasure my depotted 12/60
when my new hv probe arrived. Well, I had a chance today.

I performed open and short circuit measurements. Using a variac, I adjusted
the NST input voltage in 10V increments up to 140V input.

Here's the raw data table:
http://www.classictesla.com/temp/DepotNST_RawData.gif

Here's a graph of input to output voltage (very linear):
http://www.classictesla.com/temp/DepotNST_VinVout.gif

Here's a graph of short circuit current:
http://www.classictesla.com/temp/DepotNST_Is.gif

And finally, here's a graph of the NST's coupling coefficient:
http://www.classictesla.com/temp/DepotNST_K.gif

So, for my NST, it became extremely beefy with 1/2 the shunts removed. I
don't know what to say about others who have only doubled their secondary
current. My NST ended up at a little over 200mA (for where I normally run).
Obviously, I could send it to the grave if I pushed it too hard. But then,
I've also ran a 30 minute continuous run with it pushing 5 foot sparks and
there were no hiccups. Anyway, the data table speaks volumes.

Take care,
Bart
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