Phil,
Yea, I guess I did indeed commit a big 'no-no' by introduing more than
one modification between runs of my coil. Shame on me! ;^)) Sometimes
I just get bored and too impatient to wait until I can run her again
to hold off on trying out new ideas. LOL.
I too was wondering about the different size caps being at least one
factor for the beating. I will definitely try bypassing the resistive
ballast next time I fire her off. I really highly doubt that my
transformer/inductive ballast combo (that has already proven to be
able to effortlessly process 240 volts at 100 amps!) has reached or
surpassed its limit as far as to how large of a primary cap that it's
able to fully charge in between the RSG electrode presentations. As I
have already stated, fine tuning is really difficult for me to obtain
in my current situation, having to run her outdoors while keeping the
neighbors in mind and the fact that it takes several minutes for me to
detach and reattach my primary tap. Even if I tune her in perfectly at
low power, it may require somewhat more inductance to remain perfectly
tuned in max power mode due to the extra loading of the streamers
themselves.
Thanks for your insightful input and good to chat with you once again.
David
----- Original Message ----- From: "phil" <pip@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, April 22, 2018 4:52 AM
Subject: Re: [TCML] Finally Fired off Green Monster With New Caps.
David,
Nice to know you blew the moths out of the coil after a lay-up. I
like you always tend to consider the wastage of putting resistance in
the circuit rather than any benefits it may provide. 1.4kW is a lot
of power to use, albeit not as dramatic as loosing the same 1.4kW on
a NST coil, but none the less it highlights the importance of getting
all losses to a minimum on big coils. I know some coilers consider it
a good idea, but whether there is any benefit gained on adding
resistance may depend on individual coils though.
I hate to say it, and with all due respect to you, but I think you
have committed the cardinal sin (along with 99% of us here who have
done it at one time or another) and introduced two new factors that
could affect things, (or even three if you consider the tuning may be
out a bit), rather than just the one new factor (the caps). I just
wonder if the "beating"is now down to the different C value you're
now using; beating with the 60Hz mains (assuming it's not tuning
related). We've had beating issues with my friends (Phil S) 10" piggy
ARSG coil.
As you say bypass the resistance for now and try the caps again, with
a retune obviously, and then later maybe investigate whether the
resistance is the cause of the 80% power issue.
If it's sparked in the cabinet before, you could argue it can spark
again with out harm, as long as your own safety is not affected and
it's only occasional stress on the components.
Phil T
On 22/04/18 03:31, David Rieben wrote:
Some of you may remeber that I posted to the list an enquiry about
the suitability of GE protective power caps (2X 0.25 uFd @ 13.8 kVAC
in series) for Tesla coil operation, probably several months ago
now. Bert Hickman thought that they would be quite suitable for
Tesla coil duty, so that was good enough for me to give 'em a try.
;^) Well, between being back to working 40 hours a week and what
seems like a life time of miserable, rainy weekends, I finally got a
good day to try out those caps in my coil. Since I was replacing a
0.1 uFd Maxwell pulse cap (measured C about 0.114 uFd) with a
measured C of 0.135 uFd, the coil obviously needed retuning for
optimal operation. Since I am forced to run it outdoors in my
driveway and the primary tap takes several minutes to loosen and
reattach each time I change it, I was really only able to get a
preliminary tuning down to the nearest whole turn, but still good
enough for a test run.
I have also added 0.33 ohms worth of power resistors on one of the
'hot' 240 volt input legs, in combination with my inductive ballast
on the other 'hot' input to my pole pig since the last time I fired
it (probably at least a year by now!) I was trying to further
'smooth' the operation of the coil and further suppress any nasty
kickbacks that may find their way back to my control panel or even
my home's wiring.
Well, she did run fairly well, although it seemed like the added
resistance throttled it back a bit. I noticed that even with the
variac wheel turned up to around 80, the coil was still only drawing
around 60 to 65 amps and it seemd that this was about the 'limit' -
(it was drawing around 85 to 90 amps before without the added
resistive ballasting and with the original 0.1 uFd Maxwell cap with
the variac wheel at this same setting). Of course, even with only
0.33 ohms of added resistance, per the I2R law of joule heating, at
65 amps, thats still about 1400 watts of wasted energy that does NOT
make it to those beautiful streamers!
Also, there seemed to be more 'wah-wah' beating of the output with
my typical 300 to 350 bps roary gap setting - (noticed this more
from observing my panel ammeter flactuate than from the actual tone
of the sparks). Never-the-less, the output (and current draw) was
definitely smoother and more steady with my original setup. I tried
varying the speed of the rotary gap drive to see if I could get out
of the beat fluctuations and find a 'sweet spot', but that didn't
really seem to make much difference. So it seems that the added
resistance gave me the opposite affect than the 'smoothing' that I
was looking for.
Anywho, I will probably have an audience next time I run it and the
first thing that I will likely do is try bypassing those power
resistors. I have never really liked the idea of resistive
ballasting wasting power in heat anyway, but I have read that a
small resistive component in the ballasting does tend to smooth out
and knock the tops off of some of the nasty kickback transients. I
have still occasionally observed an occasional spark inside my
control panel where you DON'T want to see sparks! That's the only
reason that I was trying the resistive ballasting approach.
Those GE protective capacitors DO seem VERY robust, though and never
even broke a sweat - can you say 27,600 volts AC rating with never
more than 17 kVAC input??!! (plus they have internal bleeder
resistors, making them safer than the typical pulse cap) so at least
for now, I'm leaning more toward staying with them and working out
the few preliminary kinks that I am having with their operation than
changing back to my original 0.1 uFd, 75 kV Maxwell pulse cap.
Any comments or suggestions from any of the resident geniuses and/or
other experienced pole piggy coilers?
David
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--
Regards Phil www.hvtesla.com
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