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Re: [TCML] New coil modeled after Green Monster
Hi John, I was afraid that expanation would be confuseing. Here is a link
to a diagram that might help
http://www.flickr.com/photos/29248051@N02/4795675309/
Roger
----- Original Message -----
From: <jhowson4@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Wednesday, July 14, 2010 10:19 AM
Subject: Re: [TCML] New coil modeled after Green Monster
Hello,
Just for clarification what do you mean by
"Another trick I did with my choke was after each layer of wire was wound I
would switch back to
the other side before I started the next layer."
are you saying that you only built up the windings in one dirrection, like
only from top to bottom having a wire run down the length of the coil?
Thanks,
John "Jay" Howson IV
----- Original Message -----
From: "Roger Smith" <rwsmith@xxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Wednesday, July 14, 2010 9:24:37 AM GMT -05:00 US/Canada Eastern
Subject: Re: [TCML] New coil modeled after Green Monster
Hi David. when the capacitors for the primary circuit are charging, the
charging choke may cause them to charge to a higher voltage than the dc
power supply voltage . If the rotary spark gap doesn't make when the
voltage reaches its peek current will start flowing back into the charging
circuit from the primary capacitors. The dequeing or "de-Q-ing" diode will
prevent this. Here is a link to some more info on this
http://www.richieburnett.co.uk/dcreschg.html
I just noticed for the first time on Richie's
web page that we has the de-Q-ing diode between the charging choke and the
DC power supply. I guess a solid state diode would have a better chance of
surviving there than between the charging choke and the primary capacitors.
You are right that the charging choke protects the everything down stream of
it from high voltage transients. That is on of the things I like about this
set up. Your Pole pig will last forever! However the charging choke takes
some abuse and has to be made "bullet proof". On my choke I put a layer of
insulation between each winding layer. I can't remember how many winding
layers there are. I think it might be about 30. Another trick I did
with my choke was after each layer of wire was wound I would switch back to
the other side before I started the next layer. This keeps the voltage
between layers even all the way across the layer.
In the power supply circuit I have two filter capacitors that are
connected in parallel and are 1 uf each . I got them at one of DC Cox's
Teslathons. They look like they might have been power factor correction
capacitors used by a utility company. Now that I am talking about
capacitors, this would be a good place to mention that with a DC resonant
charging Tesla coil the capacitors create a serious hazard as I'm sure you
can imagine. At the very least, a person should have good bleeder resistors
across both the filter capacitors and primary capacitors and they should
test for voltage before working on the coil.
Roger
----- Original Message -----
From: "David Rieben" <drieben@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, July 13, 2010 4:15 PM
Subject: Re: [TCML] New coil modeled after Green Monster
Hi Roger,
Thanks for the info. Since this subject matter is quite re-
lavent to coiling in general, I'll keep this response open
to the entire TCML. I'm not sure I fully understand the
concept of the "dequing diode", though? I thought pre-
vention of the nasty feedback transients of the tank
circuit from feeding back into the charging circuit was
one of the main purposes of the inductive choke (6 H,
in your case)?
I do have a current limiting ballast on the LV AC side
of my control panel but I could see where the DC Res
charging setup could preclude the need for this feature.
Also, could you share a bit more info on the capaci-
tors that you use in the 2 uFd filter cap bank?
David Rieben
PS: That 10 kVA rated, 19.5 kV pole pig is a true
treasure find for an old time ARSG coiler ;^) My
pole pig is 10 kVA also, but the more standard 14.4
kV.
----- Original Message -----
From: "Roger Smith" <rwsmith@xxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, July 11, 2010 7:03 PM
Subject: Re: [TCML] New coil modeled after Green Monster
Hi Dave, Id be happy to give you some more details of my coil. I will
start with the basic parameters.
Secondary Coil diameter 12.5"
Secondary winding length 54"
Secondary wire size 19 gage
Toroud 12" x 48"
Primary Coil 1/2 " OD copper wound as pan cake coil and taped on the
13th turn
Primary capacitance .08 uf
Max Break Rate 425 bps
Max Power input so far 18 KVA
Max Spark Length so far 11 feet
Power Supply 10 kva , 19500 volt pole transformer which I I'm currently
running at an output of 17500 volts
I was running this set up with a smaller transformer and at a lower
voltage but this summer I finally hooked up the bigger pole pig I got
from Bert Hickman.
The Output from it goes straight to a full wave rectifier and then to a 2
uf filter capacitor bank. In lieu of a big variac I have a big
transformer with multiple taps
that I can use to vary the voltage to the piggy. There is no Current
limiting ballast on the AC side of the system at all.
From the filter capacitors the current flows though the charging
choke witch is many windings of # 24 gage wire wound on an "I" core for
an inductance of
6 Henrys and then I have a dequing rectifier between the charging choke
and the primary capacitors to prevent current from flowing back out of
the primary
circuit into the charging circuit. Some people have had success using
solid state diodes for dequing rectifiers but I didn't have much luck
with them. I ended up using a bunch of 8020 vacuum tube diodes in
parallel . Under the right conditions you may not need a dequing diode
but I think it reduces the risk of burning
up your charging choke.
One final comment, in theory it seems that the inductance of the
charging choke would be kind of critical but I have played around with
this a lot and it
doesn't seem to be critical at all. You will run into problems if the
inductance is too small but it doesn't seem possible to make it too big.
There might be a sweet
spot somewhere that will give you the most efferent operation but if
there is I haven't found it yet.
Roger
----- Original Message -----
From: "David Rieben" <drieben@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, July 11, 2010 9:59 AM
Subject: Re: [TCML] New coil modeled after Green Monster
Hi Roger,
Yes, I have seen pics and some description of your
coil. Very nice system you have there. Now that you
have chimed in here, I would like to get a bit more de-
tail on the DC resonant charging that you employ into
your system. As you are probably already aware, the
GM simply uses the stiff, unfiltered high voltage AC
from the pole pig to power the tank circuit assembly
and around 350 to 400 bps seems to be the "sweet
spot". However, because of the unfiltered AC nature
of the power supply and the ASRSG never being
able to fully sync with the mains frequency, I do
experience the surging (wah-wah) sound of the out-
put through much of the ARSG sped range and it seems
to me if I were to filter the HV supply to a steady DC
voltage level, it would address this issue throughout the
selected RPM range of the SG motor. I do try to finely
tweak the RSG motor speed control to blend the surging
into a more steady output but it seems to me that with a
steady DC throughput to the RSG and tank circuit, there
would be a larger average power throughput and conse-
quently, bigger sparks and hey, bigger sparks is what it's
all about, right? ;^) Feel free to contact me off-list if you
feel the details would go beyond the interest of the rest
of the list.
David
----- Original Message -----
From: "Roger Smith" <rwsmith@xxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Saturday, July 10, 2010 8:45 PM
Subject: Re: [TCML] New coil modeled after Green Monster
I have built a Tesla coil that is in some ways similar to the Green
Monster. The secondary is wound on a 12.5" diameter pvc sewer pipe, and
it is wound with 19 gage wire. It is a DC resonant charging type Tesla
coil with a break rate of 425 bps and it has worked very well.
I have never built a SRSG Tesla coil
but the one thing I don't like about them is that you are limited to
120 bps. That's less than a third of the break rate of my coil. That
means that if you are going to run the same power level as my coil with
425 bps you need to put in over three times as much energy per break.
That would be hard to do without having problems.
Roger
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