RE: NST TEST GRAPHS (was NST power test)

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

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Jim,

At 04:31 PM 1/17/2003 -0800, you wrote:
>Does any of this testing show that a simple transformer model (leakage 
>reactance, series resistance, magnetizing inductance, loss resistance) 
>doesn't adequately describe the NST operating in it's linear (non 
>saturated) regime?

It has always worked for me without exception.


>I don't know that the intersection point is truly where power in=power 
>out... it IS where apparent power (VA) is equal, but given that you've got 
>a reactive load, it doesn't say much about real power.

A capacitor can have a very high "VA"  but the "real power" is very 
low.  Richard's paper was about getting real power out of the NST.  I am 
not sure if that is the case in John's test.  However, John's graph seem to 
be showing just how powerful the underdamped resonant case can be.  I do 
wonder if he was seeing shunt saturation there!  Controlling the NST in the 
saturated shunt case would be very useful to us ;-)))  I do note the "shunt 
saturation" is just a theory and not a proven fact...

Of course, the NST main core can saturate too and limit the show as 
well...  A complex business where mistakes are "interesting"  =:O


>When the secondary VA is greater than the primary VA, it just means that 
>there is reactive power circulating in circuit formed by the secondary 
>leakage inductance, resistance, and the external capacitor.  In fact, it's 
>a good indication of resonant rise in the secondary, since that would 
>nicely explain it.

Yes!


>0.01 uF at 60 Hz would be about +j265K ohms...
>7.5kV open circuit with 30 mA short circuit output current would imply 
>that the leakage inductance has a reactance of about -j250K... (neglecting 
>the iron and copper losses, which are probably around 5-10%)
>
>
>So, the 0.01 uF case is pretty darn close to resonant.  What was the 
>voltage across the capacitor in this case?

I think it wound be high!  However, if the shunts saturated, they would 
reduce the NST's output impedance and actually damp the resonance.  Think 
about that!!!!  As the shunts saturate, the output impedance drops and 
fights the wild voltage gain and provides more output power :-))))  Of 
course, as you add even more capacitance, you may be able to bring a 
saturated shunt NST into resonance again!!  Probably want to stand back!!! :o))

This is why I recommend NST input fuses, in case the darn thing goes 
nuclear!!  There may be modes in which the thing turns into a high-power 
high-voltage bomb!!  Don't want to find out the hard way....

>While Richard Hull's measurements are interesting, his paper contains a 
>fallacy.. the shunts don't "start to come into effect"... they're there 
>all the time, along with the leakage reactance they produce.

At very low power, the magnitization current is very low and the iron my 
not act like an inductor yet.  but that is a trivial effect and detail I 
would think.

>Perhaps you really need to measure the reactive and active powers 
>separately (current probes on the cap and resistor with an oscilloscope 
>would do nicely..)

Yes, I have been holding back on the expensive toys till I am sure nothing 
is going to explode. This is one area where I really have no idea what 
could happen!!

Cheers,

         Terry