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Re: Several questions about coil.

Hi Kamil,

At 11:19 AM 12/27/1999 +0100, you wrote:
>I have made a tesla coil which is powered by 10kV 150mA transformer.
>I have a static gap (im still trying various gaps - any suggestions),
>4in secondary (770 turns made with 0.7mm wire),my primary is
>flat archimedes spiral (it's12 turns ,but of course I can adjust number
>of turns from 1 to 12). I have 23nF capacitor made of 20 beer bottles
>and salt water. My grounding is home water pipe system. My home
>installation is 10A 220V 50Hz.
>This is characteristic of my coil , and i have some questions about it.
>
>My first problem is that I connect my transformer with 1800W water
>heating device (i don't have variable transformer :-( and without
>ballast,my 10A fuse burns when the spark gap is on.
>What is real output in this connection?
>Is it much worse than with variac.

A variac allows very nice control of the power.  Your wall plug will supply
2200 watts (10 x 220) and your transformer should supply 1500 watts (10kV x
0.150).  However, the power factor is not 100%.  You transformer is like a
big inductor on the AC line and is drawing probably 50% more current than
you expect.  The voltage and current waveforms are not in-phase and more
current is needed to make up for that.  You could add a power factor
correction cap but they may be hard to find and figure out the value.
Probably the easiest thing to do is add another heater or something in line
with the transformer.  Once your coil starts to work well, this problem may
go away.

>
>Second question is about capacitors. I have made a 25nF rolled capacitor
>, and it worked, but much worse than beer bottle capacitor. What can be
>wrong with it ?

It "should" work much better...  I would check the value with a meter if
you can.  The only thing I can think of is their value is different than
the saltwater cap and the tuning is off.  One thing is that you say you are
only getting 4-5 inch sparks.  With 2000 watts input you should be getting
much much longer sparks.  Sounds like the tuning may be far off...

>
>I have also problem with toroid. I have made a 17pF toroid but it
>doesn't work properly. It's not making any sparks into the air. I can
>make only about 4-5in spark to grounded rod. I noticed that when im not
>using a toroid , but small, one inch diam. ball,
>my coil produces 3-4 in sparks into the air and also 4-5 in sparks to
>the grounded rod. Of course i want to do something to make my coil
>working properly with toroid. Which part of my coil may cause this
>problem ? Is the toroid too big, to use in my coil, or something is
>wrong?

The toroid is lowing the frequency of your secondary system.  Maybe as much
as half.  You need more primary capacitance or you need to add more turns.
You may need more than the 12 you have. 

>Of course i remamber about changing resonant frequency.
>
>My last question is about configuration of my coil. If you have any
>suggestions, what to change in my coil please share your knowledge.

Get the cap and tuning thing figured out.  You coil should put out about
four foot sparks if everything is just right.  If you still have problems,
we can compute all the values of inductance, capacitance, tuning, etc. for
your coil but we need fairly detailed dimensions to do that. 

Cheers,

	Terry


>
>Great thanks for all answers.
>
>Kamil Kompa
>czlonek-at-polbox-dot-com
>
>
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