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Re: [TCML] First coil

Hi Steve,

Beautiful workmanship!

Variacs are pretty tough beasts with significant thermal mass. Following is a link to how Staco rates theirs - other manufacturers have similar overload charts.


You should be able to push yours to 40 amps for perhaps 45 - 50 minutes at a time.


Steve White wrote:
I am restricting my input to 4.8 KW for now (20 amps at 240 volts). Everything in my power cabinet is designed for up to 40 amps except my variac. It is limited to 25 amps so it is my limiting factor although I am sure I could push it higher for short periods.

----- Original Message -----
From: "charles rakes" <crakes29@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Thursday, August 10, 2017 6:23:08 PM
Subject: Re: [TCML] First coil

Great start.  Several years ago I went to a dc design using a rotary gap
that both charges and discharges the primary capacitor.  I'm running a
7,700 volt pole transformer with a variable input.  I've only ran at about
180 vac in and getting about the same output you are now getting.     I've
got a 14,400 pole transformer ready to use, however with the coil inside
I'm almost afraid to increase my input level.  As I get older I am becoming
more careful:)  Charles


On Thu, Aug 10, 2017 at 11:33 AM, Steve White <steve.white1@xxxxxxxxx>

I just completed my first tesla coil. It is a large one. Here are the
prime specs.

* 8.6" secondary with 1410 turns
* 8 x 10 toroid
* Center line of toroid is 71" above ground plane as defined by javatc
* 12-turn primary currently tapped at turn 10.5 ( all primary circuit
"wiring" is done with 3/8" copper tubing)
* 45 nf of capacitance using 6 Maxwell energy discharge capacitors in a
series-parallel configuration with load balancing resistors
* 10 kva pole pig running at 14,400 volts
* Sophisticated control cabinet including 25-amp variac, ballast, RSG
phase control, breakers, contactor, PFC capacitors (currently about 150
uf), volt meters, current meters, EMI filters, MOVs, lockout switches,
indicator lamps
* Hand-made ballast with adjustable air gap currently set for 20 amps
(similar to Richie Burnett's)
* Rotary spark gap with one stationary 5/16" tunsten electrode and 4
flying 1/8" tungsten electrodes turning at 3600 RPM
* HV leads made from 10,000 volt AC Belden test lead wire threaded through
PVC tubing for additional insulation. This is all surrounded by grounded
copper braid for uniform field distribution and to protect against streamer

I made extensive use of javatc to design this coil. I was confident in
starting with a large coil because I am a retired electrical engineer thus
I had a lot of knowledge about electrical theory. I also own my own mill,
lathe, bandsaw, oscilloscope, and signal generator. Finally, I had the
funds to muy and/or build quality parts.

Even though this was my first coil, surprisingly it worked the first time
that I fired it up. I am currently getting 6.5 foot power arcs. It should
be getting up to about 8 feet according to javatc. I am continuing to
adjust the primary tuning. I think I need to go a little lower in frequency
to account for streamer capacitance.

I do have a few questions concerning RF grounding.  I currently have a
copper-clad steel rod driven 3 feet into the ground for the RF ground. This
is as deep as I could drive it. I may try a water boring rod to try and get
deeper. I currently have the following connected to the RF ground.

* Strike rail
* RSG motor chassis
* Copper braid shield around HV leads
* Copper braid around RSG power cord
* Pole pig case

Does this sound about right?

Steve White
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