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Re: [TCML] Need some advice on 150kva sgtc

Wow, that indeed sounds like a well designed charging reactor for that system! Amazing.
Do you have some specs of your rotary also? With 700bps I guess you are using one big disc with at least 10 electrodes to keep the speed and therefore mechanic stress on the disc relatively low. Or are you using a full metal disc + insulating shaft? That would make higher speeds possible with not so much electrodes. What is the diameter of your electrodes?
By the way, what is your experience with very low break rates? Did you try out, at which speed the spark gap ignites a "firewheel"? Your reactor is only 500mH so I think low break rates are particulary critical, because the current through the reactor rises at a very fast rate, when the power supply is short circuited accros the closed gap through the reactor and it opens to slow at low break rates? What are your observations? My system is designed for 400bps with a 12,4H reactor, but until now I didn't dare to gow below 200bps altough there where no signs of any problems, I guess I could go even down to 100bps, will have to try this :) 

Regards,
Stefan
----- Original Message ----- From: <vam@xxxxxxxxx> 
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Friday, January 02, 2015 6:45 PM
Subject: Re: [TCML] Need some advice on 150kva sgtc



Stefan thanks for your observations.
The reactor is wound around a 50 kva 3 fase core with the middle leg
removed. and cut in halve to introduce two air gaps. it has 10 sections on
both legs with 2.5^2 mmm and 200 turns, so about 2000 turns. i lost the
calculations, but it was the most challeging part to calculate. it will
not saturate.
I'm well aware of the 10 amp charging current.
i choose a large primairy capacitance to compensate for the relatively low
32 kv end voltage. i think that's pretty high anyway.
The coil should work nicely at 200 bps and anything above should be a bonus. 
I added a new post with a hopefully working link to a picture of the coil.



Maybe you have some saturating issues with your charging reactor, is it
designed properly to handle the massive charging current without
saturation?
Taking your numbers, that gives a maximum power of 143kW @ 700bps and
therefore a charging reactor inductance of only 518mH. The RMS charging
current through the choke is 9,9Amps. Designing such an inductor is a
challenging task, also needs some thick wire to handle 10Amps of charging
current.

Another "problem" I see in your supply transformer, with only 10kV it
leads
to big currents, primary capacitance and much to high break rates in the
whole system, for processing the desired power of 150kW. For such a big
system it would be better to use an AC supply voltage in the range of at
least 15 or better 20kV. Your 80kV caps wouln't have any problems with
that.
Regarding maximum break rate, different coilers also reported, that there
is
no big improvement in performance above the 400bps level.
Regarding spark gap, in my opinion it is better, to not exceed 400-450bps, 
but therefore using other tricks to achive a good dwell time and gap
opening
speed. By the way, when using more than 4 series gaps in the rotary, it
also
becomes a problem to "ingnite" the charging system, when using only 10kV
AC
(~14kV DC).

Regards,
Stefan

----- Original Message -----
From: <vam@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Friday, January 02, 2015 9:43 AM
Subject: Re: [TCML] Need some advice on 150kva sgtc



Hi Carlos.

The streamer length increases significantly from 100-200 bps. 200-600
there is only a slight increase, probably ads only 50-70 cm to the
streamer length.
The 2.2kw sparkgap motor can't get the disc to spin over 700 bps.
The 125 amp fuses can only take 700 bps for a short while before they
pop.
The coil jumps to two steady streamers at this power level.
We had primairy to secondairy flash over at 700 bps, so the coil is in
repair now. This led me to believe that the coupling is already too
high.
It's .2 acoording to javatc. Playing around with the coupling is not so
easy with a 250 kilo secondairy and topload. We think about installing a
carjack or something like that.
The sparkgap quenches at second notch with airstreamers and firstnotch
in
ground strikes.
Highering the coil will probably help some because it easily finds it's
way to the floor. We might ad a smaller topload so we can higher the
main
topload.


It would be intersting to see how arc length would improve if you lift
the coil up a bit off the ground, and increase the BPS rate.
Coupling is also pretty important on big coils...
Have you experimented with increasing the coupling at all?

Carlos

On 2015-01-02 08:13, vam@xxxxxxxxx wrote:

You got my message spot on Carlos.
The coil produces constant streamers about 20- 23 feet, or 6 - 7
meters.
It's very impressive. But i did make a  coil with 1 m winding length
before, producing 3 meter sparks at 20 kw.
so i expected around 10 meters with this set up. but 7 seems the max.


Big machines like this are typically less efficient than there
smaller
brothers and sisters.
I have not taken the time to run the numbers on the info you
provided,
but if the system is well balanced and in tune and pulling 40kva, I
would expect to see 20-25 foot long arcs at minimum.
The height of the coil will also be a limiting factor to some
degree...

I assume from your question that you are not happy with the
performance
or it did not meet your expectations?

Kind regards,

carlos

On 2015-01-02 06:03, vam@xxxxxxxxx wrote:

Me and some friends built this coil. It's total height is 5 meters.
the
donut is 2,60 by 60 cm. the coil is 65 cm dia with 1200 turns of
2.5^2mm
installation wire. about 3.6 meter winding length. Cap, DR resonance
100nF, 80kv 4 in parallel.
We feed it with a 180kva 10kv yz5 transformer. Rectify the lot to
16kv.
ballast ensures 32kv on the cap. at 200 bps we draw 50-60 amps per
fase.
so roughly 40 kw. Max bps is 700.
Now the question. What kind of spark length should be possible from
this
coil?

Picture of the coil.
https://www.facebook.com/photo.php?fbid=671287332969054&set=a.110176789080114.14601.100002633816524&type=1

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