[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
RE: NST TEST GRAPHS (was NST power test)
Original poster: "John H. Couture by way of Terry Fritz <teslalist-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
Hi Kurt -
Congratulations on the expansion of the data from Richard Hull's tests using
Excel. Hull's data has provided a good starting point for coilers to study
the NST loading problems. Your graph results show how complex the loading of
NSTs can become. I hope you will be able to go further with investigating
the NST loading mysteries and use your skills with Excel to produce more
graphs. This would check the tests and graphs that I have made, something
that I have not been able to do before due to lack of this type of
information. One of my graphs made with Quattro is shown at
This graph is with an NST and only a capacior for a load. However, graphs
with loads using combinations of both resistors and capacitors are similar.
My tests and graphs appear to point out that sometimes the Va Input and
Output curves intersect. This point is when the input power is equal to the
output power. It also appears that this is a point of a maximum for both the
VA and the active watts. If this is correct the intersection of the curves
would also indicate an optimum operating condition and maximum overall
efficiency. I believe this is all new information to coilers so will have to
If you or other coilers decide to do these NST loading tests I recommend as
a start that you use something similar to what I used. With my tests the
capacitor was .016 uf/30 KV connected with resistors varying from 8 Kohms to
250 Kohms. I connected the capacitor in series with the resistors. I
measured the voltage, current, and wattage of the NST primary and the
voltage (electrostatic meter) and current of the secondary circuit. The Va
and Power Factor for both the input (primary) and output (secondary) were
One of the graphs I made was with resistance as the X axis and the Va as the
Y axis. This produced two non linear curves Va input and VA output that
crossed at a point on the graph. Other graphs I made included watts in vs
watts out, sec volts vs sec amps, and sec volts vs sec VA.
I found the graphs very informative and gave me a rewarding look into the
operation of NSTs when connected to various combinations of capacitive and
resistive loads. This information can be used when powering Tesla coils
with NSTs. In fact the pole transformer or MOT with ballast is a similar
source of power where the current is limited. Would the combination load of
resistor and capacitor (Tesla coils?) produce similar graphs?
I hope you, Terry, and other coilers will find the time to make at least
some of the NST loading tests and graphs because this information would be a
great help to all coilers. There is much to learn about these mysterious
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Saturday, January 18, 2003 2:59 PM
Subject: Re: NST TEST GRAPHS (was NST power test)
Original poster: "Kurt Schraner by way of Terry Fritz <teslalist-at-qwest-dot-net>"
Richard Hull's valuable measurements are indeed easily and satisfactory
represented by a simplyfied transformer model, as is always implicitely
used by coilers, when calculating a resonant primary cap: an ideal
transformer connected to leakage inductance (as seen from the secondary
side). With optimized parameters, for example the 5/30 NST:
U2o/U1=42 485 H i2 (i2k=27.6mA -at- R=0)
o---------L ¦¦ L------LLLLLLL---->--o------.
L ¦¦ L ^ ¦
L ¦¦ L ¦ R
U1=120V L ¦¦ L U2o=5.03kV U2 R
(60Hz AC) L ¦¦ L ¦ R
L ¦¦ L v ¦
o---------L ¦¦ L--------------------o------.
One important thing, which is missing in Richard Hull's measurements, is
the short circuit current i2k (->when R=0), which is 30mA, by the nameplate
of the transformer, and had to be slightly modified to 27.6mA, for best
representation of the tests. I had a closer look at the data, using Excel
Relevant for this "closer look" was, to verify, that the whole range of
operation of this NST can be represented with a single value of the
stray-inductance. I guess, sometimes it goes forgotten, that the nameplate
current of an NST is the short-circuit current, if not mentioned otherwise.
If extending tests, like the one of Richard Hull, carefully including
capacitive loads in the investigation may add to the value of the results
for TC-coilers. More elaborate models, including copper and iron losses are
opened, when including a wattmeter in the investigations.
Tesla list schrieb:
>Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>"
>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.
>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..)
> From a power transfer standpoint (which might not be what you want), you
> want the "conjugate match".. that is, considering the source as a series
> combination of an inductor (leakage inductance) and a resistor(copper
> losses, in this case, referenced to the secondary side)
>you'd want the load to be the equivalent of a series resistor of the same
>value and a capacitor of equal reactance.
> (magnetizing inductance and core losses don't apply for the matching
>In your setup, you've got a a parallel RC, which you'd need to transform
>(mathematically) to the equivalent series circuit..
>What we want in a TC, though, is a bit trickier.. it's not a steady state
>sinusoidal circuit, but, rather, a transient one, where you are charging a
>capacitor through an inductor and resistor. I suspect that a time domain
>simulation might be a better way to approach the problem.
>The measurements of NST output with RC loads, though, will give you a good
>way to confirm that a linear model of the NST as a resistor and inductor
>is a good one.
>>Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
>>I have been doing tests too :-)) Although still very rough draft like, it
>>It is not done yet, but I thought I would mention it now for
>>suggestions. I could only get 260VA out of a 360VA NST using just
>>caps. Any ideas are welcome ;-)) It is all set up and just waiting.