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Re: [TCML] Questions on grounding


I took a look at your coil.  Looks pretty nice for a first coil, certainly
much better than my first.  I saw one thing that hasn't been addressed yet
that concerned me.  You say, "*High voltage 15,000 volt wire used
everywhere."*  I'm assuming you're talking about GTO which is usually #18.
If you are using this for your primary leads you should remove it and
replace it with the thickest wire you can get your hands on.  #18 will be
very lossy, and could quite possibly catch fire due to the high primary
currents.  I would suggest that you use at least #10 for the primary leads,
since the length you need is rather short you may as well shoot for #8 the
price difference is not that great.  Assuming you have the gap across the
transformer bushings, you can still use GTO to connect the transformer to
each side of the gap.  Every other connection should be heavy gauge wire.
Using GTO isn't really saving anyone from being shocked since there are
plenty of other exposed surfaces that are at several kV when the coil is in

-Phillip Slawinski

On Wed, Apr 15, 2009 at 10:02, bryan_es@xxxxxxxxx <bryan_es@xxxxxxxxx>wrote:

> I agree with all of the above. It's been a while since I built an NST coil
> but when I did last, I created a nice earth ground by digging a 5 foot wide
> by 3 or so foot deep hole and burying a few turns of copper tubing in it. I
> just grounded my NST to house ground thinking it was good to keep them
> separate. No real science to support using separate paths but the coil
> performed well. It was a 4 inch coil using a couple roof flashing caps I
> built and a static gap. Don't recall the exact performance details but I
> want to say sparks in the 3-4ft range were pretty common using a 12in
> aluminum tap toroid.
> I remember reading somewhere that if you have to fall short on your coil
> somewhere, the base ground is the last place to do it...
> ________________________________
> From: bartb <bartb@xxxxxxxxxxxxxxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Sent: Tuesday, April 14, 2009 8:53:52 PM
> Subject: Re: [TCML] Questions on grounding
> Jay (and Joe),
> You do need a dedicated ground separate to your house ground of which your
> bottom secondary should certainly be tied to. With the NST, you can either
> connect the case to house ground or to this dedicated RF ground. But,
> realize that if you connect the case to house ground, the "house" components
> will have nasty RF spikes and transients running directly to all of your
> appliances in the house. If you tie the NST case to RF ground and end the
> house ground back at the control cabinet, you will have far less electrical
> mess at your appliances. The choice is yours.
> Anyone stating to "never connect the NST to the secondary RF ground" I
> strongly disagree with. Look in the TCML archives as there are plenty of
> discussions regarding this very issue which we've discussed many (many)
> times (only a month ago I believe was the last blurb).
> Take care,
> Bart
> jhowson4@xxxxxxxxxxx wrote:
> > First of all I am thinking that you need to connect the bottom of your
> secondary NOT to your NST. you need a separate ground for called the RF
> ground for the secondary.
> > The case and ground of the NST should be connected to your house ground
> and never connected to your secondary.
> > making the toroid really smooth will increase spark length. I have found
> that covering the tubing with plaster, sanding it smooth then covering it
> with aluminum duct tape, and smoothing that over with a spoon works really
> well. it is also beneficial to fill the interior of the tubing with some
> expanding foam to help prevent it from being crushed so easily. Here is a
> pic of my coil with the closest pic of the top load that I had.
> http://i139.photobucket.com/albums/q295/JHowson/DSC06682.jpg
> > Jay Howson
> > ----- Original Message ----- From: "jocatch" <jocatch@xxxxxxxxxxx> To:
> tesla@xxxxxxxxxx Sent: Tuesday, April 14, 2009 9:35:05 AM GMT -05:00
> US/Canada Eastern Subject: [TCML] Questions on grounding
> > Hello. I have built my first coil using standard parts and dimensions and
> have fired it up and so far I am producing sparks but only about 12" long. I
> am using a 12KV nst with .0125uf mmf, 13 turns of copper tubing as primary
> and 20" of #28 magnet wire on a 4" form with aluminum cloths dryer ducting
> for the toroid
> > My questions concerning grounding. I have read alot about discharge spark
> length but not much regarding how to measure it. Above I said 12" discharge
> spark length, that was to a key ring held at the end of a boom stick handle.
> Should the metal object that I am drawing the spark to be grounded? To earth
> ground? Right now nothing is grounded to earth or electrical ground. The
> bottom side of the secondary coil is connected to the metal case of the nst.
> Should the secondary coil and nst be grounded to earth ground?
> > Lastly, the aluminum toroid is discharging all around its circumference.
> I know the fewer discharge points on the top load, the bigger the discharge
> length will be. If I tape the toroid with aluminum tape to produce a
> smoother surface, will it help?
> > I have a web page showing photos of my first tesla coil before I recently
> updated it to copper tubing and new toriod. The web page shows the old
> primary wire coil and old topload. I will post new pictures of the update
> soon.
> > http://www.joecool.org/joe_s_tesla_coil.htm
> > Thanks for your help.
> > joe _______________________________________________ Tesla mailing list
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> >
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