[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TCML] Depot NST Measurements

Not for these particular measurements (topology of getting to know your transformer). I try to make these measurements if possible on transformers but usually only at it's rated input. This particular (10V increment) testing I did mostly out of curiosity.
For looking say at an transformer running the coil, secondary base currents, etc.., then you do need a current transformer and best to have one with the BNC connection ready to go. For a CT say with a good 2" hole is nice as you can fill the center with insulation so the hv wire passes only through the center. You have to use HV common sense with CT's also (like anything else we do). 

Take care
Bart

Phillip Slawinski wrote:

Ahhh, I see.  So you don't have to have a fancy clamp meter?

On Sun, Jun 29, 2008 at 8:25 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:


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
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla




_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla




_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla


_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla


_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla