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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