tesla coil power ?! (fwd)

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Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Sat, 22 Sep 2007 12:23:59 +0100
From: Chris Swinson <list@xxxxxxxxxxxxxxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: tesla coil power ?!

Hi all,

After messing around with many coils, I found that some of my secondary 
coils were sparking when near my tesla coil in operation. After some 
tinkering about I managed to light up 3 100watt lamps from 3 secondary coils 
placed about 1 meter away from the tesla coil. The lamps did not dim as each 
one was lite so appears to be a fair amount of RF radiated there.

Though trying not to get shot down here, but it was only a 500w tesla coil 
in the first place, I did not have enough room to physically place anymore 
secondary coils there but this suggests that 3 more coils would output 
600watts ?!

I spent a while lot of time crunching this , even with low power testing on 
12V coils. From what I can work out, from a transmitter coil to the receiver 
coils there seems to be over 90% loss in voltage. However moving the 
receiver coils closer to the transmitter starts to drag down the voltage, 
though does not seem to effect it more than 1% or so. Moving further away 
the voltage drops but the 100watt lamps remain lite until all of a suddon 
the lamps just go out just over about 2meters.

Even though I can't measure the voltages, I would guess that 10KV impressed 
upon the receiver coils would have to have 10mA of current, for 0.01A x 
10,000 = 100watts. If we take the transmitter power as 100,000volts then we 
have lost like 90% of the voltage. So this must mean 90% loss ? on this 
basis the transmitter would have to output 90times higher the wattage ?!  if 
we have 10,000watts and loose 90% then we only obtain a few watts output 
kind of thing.

Further to the problem, adding 2 more receiver coils does not seem to effect 
anything. If power must divide between coils like a regular transformer then 
the wattage on the transmitter would be near unthinkable.

Going to a small 12V test. I can obtain about 0.1V output per receiver, 
actually this supports my post on plasma globe power also. where you can 
draw about 0.1mA per receiver but only the first receiver coil drops the 
voltage on the antenna. Adding more coils has no effect on the transmission 
voltage.

Going back to the tesla coil testing again, each time you actually add a 
receiver coil, you would assume it would shunt the transmission , like a 
faraday cage. Though it actually boosts the transmission "range" by about 
25%.

The problem is with these results is the more receiver coils you add, the 
stronger the transmission actually seems to get. Running 2 coils side by 
side or any point around the transmitter has no effect on anything ?!

If there was 50% coupling to the transmitter then once the second 100watt 
lamp was added the first one would dim, but it does not. As the voltage has 
lost like 90% over the distance, then even 10% coupling over 2 receiver 
coils is 30% loss overall, but the lamps did not dim.

I then obtained some X-ray machine diodes, had to have a long talk to their 
sales guy first though :-(  Special HV HF diodes so I could convert the 
250khz AC to DC. I could run window wider motors there no problems. I then 
also charged up a range of capacitors, much like my plasma globe tests. I 
can't remember the values now, but after I crunched the numbers there would 
have to be 100watts to charge the capacitor to a voltage over 20 seconds. I 
got these figures verified by some people on the electronics forum and 
several electronics engineers at the company I used to work with. So the 
100watts power seems to be real.

I ran out of space and funds so I could not try anything further :-(  Even 
so 500watts input and 300watts output does not seem very exciting. Though it 
makes me wonder how many coils could be powered in this way. As more coils 
increase the transmission range then it seems to suggest the more coils 
added , the more efficient the system becomes.

I plotted whole charts of data and gave up. In fact if you assume 10mA is 
the baseline current figure then 10mA at 100KV is a lot of wattage. If the 
receiver coils were coupled enough to obtain power then the lamps would dim 
each time one was added. Though if the coupling is only like 1% then you 
could have 10 receiver coils which would load in a way to output 90watts per 
coil, which is 900watts x 10coils = 900watts. The problem is I was in 2minds 
about posting this to the list, as it implies 900watts output with only 
500watts input.

I latter reversed the testing and ran on 250watts power. With this setup I 
could  only light up 25watt lamps at best. So as the input was cut down by 
50% the output wattage was cut down by 4times. On this basis, if I increase 
to 1KW input, then I would obtain 4times the output wattage.  Also 4times 
the output also increases the range. I had problems with the 250watt system 
as the receiver coils were coupling to the transmitter coil and causing it 
to go off tune which messed everything up.

It is hard to work out what is going on here. has anyone here done anything 
along these lines before ? I know Richie lite up I think a 25watt lamp via 
RF, 2 people holding it at one of the Corby events I think. Though that was 
a "untuned" setup. If you run the lamp between 2 toriods, one in the 
"transmission range" and one outside (3 meters away) then you can light up 
25watt lamps. Though it works a lot better to ground one end of the lamps 
and obtain 100watts output instead.

I wonder if there is  a sub resonance between the transmitter and receiver 
coils which is the reason the transmission range is increased. Placing 2 
coils side by side is hard to work with due to the high voltage involved. It 
was unclear if the lamps were brighter with 2 coils next to each other. 
Though either way it seemed to have little effect.

Taking things a little further. I built a larger primary coil and placed 3 
secondary coils inside. Each coil gave some good output , though I forgot to 
document the results, but seemed to work very well for powering multiple 
secondary's within the primary. Arcing between coils made testing very 
problematic anyway.

If the transmitter is not coupled and has all these losses, then the 
transmitter is not being loaded ? if so it would mean we could obtain 
100watts almost unlimited times ?!

I did some 12V testing again, over 15cm there was like 99% loss. Though 
using a 1K resistance and measuring the voltage, I could obtain there was 
about 0.2mA of current at about 0.1V. This was without a transmitter coil. 
Actually I just ran a meter of wire from my signal generator and it 
increased efficiency about 4 times.  I don't know how much current was 
involved, but there was nothing connected to the signal generator other than 
the cable. Each coil at 99% loss did not appear to load the antenna. At 
least he voltage never dropped. Well it did a fraction but was so small was 
not much. In anycase adding more coils did not appear to drain the voltage 
any further.

While 0.1V is uninteresting at fractions of a milliamp, however at 1million 
volts 0.1mA is 1KW. As my 100watt tests appear to operate at 10mA then as 
the voltage increases then so does the amps. I plotted in that each time the 
voltage doubled the wattage output would go up by a factor of 4.  In 
anycase, it would seem at least 100KV is needed to obtain any sort of 
results. Anything below 100KV you have to move closer to the transmitter to 
obtain any power. Though anything closer than 1 meter starts to become a 
real problem for many reasons. Though it appears to me that the arcing and 
de-tuning are the main factors, not so much a drop in transmission power.

In fact if you move one coil  as close as you can get without the system 
going out of tune, you can easily blow 100watts lamps. I had a box full of 
blown lamps at the end of the week. Good thing is though they glow purple 
when burnt out :-D

All being said and done, that's all the facts and figures in a "overview" 
kind of way.  Figures are the best I can come up with to fit the results. 
They could be totally wrong though even so I can light up 300watts worth of 
lamps form my tesla coil. The interesting test would have been to add 3 more 
coils, but something I just could not do unfortunately. So reason why I 
posted my results to see if anyone else had done anything interesting along 
these lines before ?

Very confuzzeld again, but nothing new there.

Chris