That looks a LOT like mine, before I changed the Synchronous motor for a 3 phase motor with a VFD.
From: Phil <pip@xxxxxxxxxxx>
To: 'Tesla Coil Mailing List' <tesla@xxxxxxxxxx>
Sent: Tuesday, April 14, 2015 3:53 AM
Subject: Re: [TCML] Fram the new guy.
Thanks David.
For others here is David's link in unbroken format:
http://www.teslatechnologyresearch.com/rotary_spark_gap.htm
(Surprised at how big a gap they run)
Phil
-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of David Rieben
Sent: 14 April 2015 01:28
To: Yurtle Turtle; Tesla Coil Mailing List
Subject: Re: [TCML] Fram the new guy.
Adam, Phil, all,
Yes, Adam understands what I was trying to explain. Since there were 2 pairs of 2 stationary electrodes, set at 180 degrees apart on the disc, and the 2 pairs of stationary electrodes were bridged to form a series 4 gap SG with each presentation of a flying electrodes between each stationary pair, then each flying electrode was getting hit twice per single revolution of the disc, instead of once. Whew, Adam's right, a picture would be helpful ;^) Here is a pic of a RSG with the 2 pairs of 2 stationary electrodes, set at 180 degrees apart on the disc (first picture):
Tesla Technology Research -- Rotary Spark Gap
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| Tesla Technology Research -- Rotary Spark Gap |
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| View on www.teslatechnology... | Preview by Yahoo |
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Obviously, when the flying electrodes "line up" between each pair of stationary electrodes, the gap fires across 4 air gaps at that moment and consequently, each flying electrode will see 2 firings per disc revolution. What I did was remove one pair of the stationary electrodes.
David
On Monday, April 13, 2015 9:27 AM, Yurtle Turtle via Tesla <tesla@xxxxxxxxxx> wrote:
I think he meant you now have twice the thermal mass to dissipate the heat. It all depends on how you configure the RSG. My first RSG used a copper ring and two stationary gaps, on on each side (nothing on the back of the disk. This used two rotating electrodes, but resulted in two sparks. If your rotary electrodes protrude the disk, you can use two stationary gaps, one on each side of the disk (front and back). Still just two sparks per presentation, and the heat on the static gaps is the same, but you now have only one rotating gap taking the full load. I currently have a, rsg with four static electrodes, connected in series, and eight flying electrodes.
You're correct, that if I understood, the bps doesn't change. There are many different configurations though.
Pictures are useful for conversations like this.
From: Phil <pip@xxxxxxxxxxx>
To: 'Tesla Coil Mailing List' <tesla@xxxxxxxxxx>
Sent: Monday, April 13, 2015 7:16 AM
Subject: Re: [TCML] Fram the new guy.
David,
You wrote>>
----------------------
"Each flying electrode was now indeed seeing 2 firings per rotation instead
of one but, each firing should also have had only half the thermal energy to
dissipate, since the spark was being commutated 4 ways per firing, as
opposed to 2!"
----------------------
I'm a bit confused on how the addition of two extra stationeries' was giving
"2 firings per rotation instead of one" over 4 gaps. What do you actually
mean by "firings" - the bps rate?
An extra pair of electrodes in series is sometimes the approach used on
RSG's, but that wouldn't double the "firings"
Did you place the second pair at 180 degrees to the existing pair, if so
only one or the other would fire, or where the second pair placed at some
position, (like 90 degrees away)?
Phil
======================================================================
======================================================================
Original post:
Multiple spark gaps, as opposed to single spark gaps, facilitate better
quenching by dividing the generated thermal energy into smaller portions at
each gap. Too much thermal energy for a gap to dissipate within the given
time constant effectively kills arc quenching, which shuts off the resonant
switching, and consequently, the spark output of the coil. Of course, such
added thermal dissipation features, such as forced air flow, can facilitate
much increased quenching for a given gap design, too. However, each gap also
introduces its own resistive losses to the flow of resonant tank currents,
too, so when you have too many seriesed gaps in proportion to the power of
your system, these additional losses end up being subtracted from the spark
output as well. Kind of a balancing act.
As an example, my multiple kVA, pole pig driven ARSG system started with a
simple rotary gap with 8 flying electrodes and 2 larger, 1/2" diameter x 3"
long, heat sunk, stationary tungsten electrodes (effectively 2 operational
series gaps, when firing). The naturally generated wind currents generated
by their ~3000 rpm rotation seemed to provide adequate quenching, even at 12
to 15 kVA throughput! When I introduced a second pair of stationary
electrodes, for a total of 4 stationary electrodes and effectively 4 gaps,
when firing, it seemed that although it was not that noticeable, the output
was slightly diminished and less smooth (although still handily over 10 ft
discharges). The real problem though was that now the 8 flying electrodes on
the rotary disc were no longer staying cool enough from the generated wind
flow of their movement to prevent them from actually starting to blister the
neighboring G-10 material of the rotary disc! Each flying electrode was now
indeed seeing
2 firings per rotation instead of one but, each firing should also have
had only half the thermal energy to dissipate, since the spark was being
commutated 4 ways per firing, as opposed to 2! Yet, there was obviously more
resistive gap losses to contend with, and consequently more heat, which
manifested itself as the new symptom of blistered G-10 in my rotary disc,
and also a slightly rougher and reduced spark output from the coil. I ended
up adding aluminum shaft collars to the 3/8" diameter x 2" long flying
tungsten electrodes on each side of the disc, to introduce more thermal mass
to them. This did improve the excessive heat buildup problem, but I also
finally ended up going back to the 2 stationary electrodes and my spark
output seemed to improve once again.
If it ain't broke, don't fix it!
David
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