Re: my first personnal tesla coil
Finn Hammer, Sun Oct 08 2017, 03:11PM

Pierre,

You seem to be doing allright, there.
For a 2.1 meter spark you need at least 70cm of secondary coil, I would recommend one meter of secondary for that, so you might find that a longer secondary would be better.
The topload should follow, so that the major diameter is equal to the secondary length.
These are just numbers that have shown to produce great results, less is usable too.
Nice to see someone building a spark gap coil with mot power.
Cheers, Finn Hammer

Re: my first personnal tesla coil
paulj, Sun Oct 08 2017, 04:28PM

Hello,

Thanks for the compliment, I hope it will work, because for me the simplest coils are the most robust

the goal is to build the most powerful coil for installation in a house,

I applied myself to the security components because it is very strict in France in public places.

ps:

the tube is pvc
the screws are nylon
the plates to plug the PTFE tube to support ozone and high voltage and wear time.
the base varnish (class 220) is made of special acrylic for use in high voltage and a large layer of polyurethane varnish has been applied (7 coats of varnish)

I am assured that no sparks are formed in the tube by placing any conductive wire inside the coil. and the screw above the secondary is not connected to the future toroid.

I've been working on it for years, for the 70 cm secondary coil, it's a 80 cm reel I have, do not rely on my JAVA, it's altered.

the only thing that scares me is the capacitors, I will use Maxwell 35349 brand new (very rare in France).

I will try to give you more information in the next month.

Re: my first personnal tesla coil
Sulaiman, Sun Oct 08 2017, 06:44PM

Looks like you will have a very nice TC.

just a few minor side notes :

Long after you have forgotten reading this note,
you will find that a heavily insulated secondary can build up a shocking ammount of static electrical charge

It looks like you have a steel nut at the bottom of your secondary,
if so then it will heat by induction from the primary coil.
I have melted pvc like that.

Regarding capacitors;
polypropylene foil/film/foil capacitors are normal for most coilers
but at one time there seemed to be a lot of sgtc made in Germany successfully using much cheaper metallised mylar (MKT) primary capacitors.
I can not think of a url at the moment but I'm sure google will get you started.

Snubber capacitors for high power thyristor and IGBT 'blocks' have also been used.

Re: my first personnal tesla coil
paulj, Sun Oct 08 2017, 09:36PM

I knew there was a risk of induction, the nut is in fact the earth plug, and the screw on it is also made of nylon.

But

  the 4 screws at the top of the secondary coil are made of nylon, but for the base there are 4 steel screws because the base had to support the toroid and the secondary circuit because I designed it to be attached to the ceiling, a building.

For capacitors, I think to put them in parallel to modify more easily the turns of the primary coil.

Re: my first personnal tesla coil
paulj, Sat Nov 11 2017, 03:21PM

Hello

here is the continuation of construction

the spark gap is finished, it's an improved copy of Terry's spark gap
- 1/4 inch pure tungsten electrodes
- The rotor is made of PTFE to withstand the heat and the ozone vapors, like the bakelite of the support which is a good insulator. I wanted to use cheaper polyethylene, but it not seems to be badly resistant to ozone and heat over time.
- a simple dryer motor animates the rotor.
- aluminum busbar for connections

I chose this design rather than a synchronous motor spark gap to have a total control over the spark using a variac, I can pass u, but also for its low price, and also its ease of construction.

the fan will be oriented differently than in the photo.

I tested it at 2700VA without capacitor, no problem for now

Finally, here is a picture of the set currently the toroid is not finished.
on the primary coil, it still lacks the strike ring.



PS: Finn Hammer: I respected what you advised me, the major diameter of the torus is equal to the length of my secondary coil.

Re: my first personnal tesla coil
Sulaiman, Sat Nov 11 2017, 07:21PM

A Request

I am of the opinion that with a flat spiral primary coil
inverting it changes the likelyhood of arcing from secondary to primary.

so

Could you please make provision for the flat spiral primary to be operated either way up
with little effort required to change orientation. ?

To determine for yourself if this is true or nonsense.


P.S. the primary turn spacing looks to make an adjustable tap difficult.

Re: my first personnal tesla coil
paulj, Sat Nov 11 2017, 08:36PM



Hello Sulaiman

I misunderstood (my english is very bad, sorry)

reverse?
- invert the output poles of the primary circuit to the primary coil?
- to make a selenoid coil? (very bad idea)

Could you detail of yours request please?

Ps: I have about 1.2 cm spacing between the turns, it is temporary, with my two maxwell 35349 in parralel, I would not need so much turns.

everything will depend on the true resonant frequency of the secondary circuit

Re: my first personnal tesla coil
Hazmatt_(The Underdog), Sun Nov 12 2017, 05:48PM

A flat spiral coil that is very dense is the best for a SGTC.

If the turns are not dense, then the magnetic lines of flux that are being generated from the ringdown are not as concentrated, so you basically radiate your magnetic field "away" instead of into the coil. I goofed on a coil I built for a customer with too much spacing between turns and the output suffered as a result.

You actually do not want any tuning taps, why? Because every extra inch of primary is lossy and reduces the energy in the primary inductor. Ideally (and this is the way I do it now) it is all primary and cap, no extra lead length at all. Any leads will have 200-300A pulsed and that energy is just being wasted in your leads ultimately reducing arc length.

Instead, you want to fix your primary and trim your secondary to be in tune, it takes a while but you have better performance when you're tuned within 10 Hz of the primary resonance. I do that with a synthesized generator like the HP 3325B which is not too expensive these days on ebay.

An inverted spiral, so Sulaiman means the start of the winding is parallel to the start of your first turn at the base of the secondary coil and the subsequent turns are lower, so it descends and the turns progress outward.
You can do that, but again you will have less flux density if you do it that way unless the angle is very shallow (<15 degrees), at that point the flux should approximate a flat spiral.

I always get criticized for my comments so go ahead, i'm not going to let it bother me.

I have gotten good performance out of flat dense spiral primaries and have not really needed a strike rail for protection, but that is with the caveat of running under 1500 VA, and a coil H/D ratio of at least 3.5.

Remember, the details are important with these things!

Re: my first personnal tesla coil
paulj, Tue Nov 14 2017, 07:29AM


I understand better,

According to your advice, I will start tests with a flat spiral, I will see if I evolve on an inverted spiral.

I will finish the secondary circuit first and start the measurements.


Paul

Re: my first personnal tesla coil
paulj, Sun Nov 19 2017, 11:35AM

Hello,

for fun, I took my old features on JAVA TC and I changed the specifications of my primary capacitor and coil.

As I don't know the reverse voltage that can support, I put them in parallel to distribute the current so this is 0.14uf

old spec:
J A V A T C version 13.2 - CONSOLIDATED OUTPUT
19/11/2017 à 12:13:08

Units = Centimeters
Ambient Temp = 68ºF

------------------------------------------- ---------
Surrounding Inputs:
------------------------------------------ ----------
2500 = Ground Plane Radius
2500 = Wall Radius
3800 = Ceiling Height

------------------------------------------ ----------
Secondary Coil Inputs:
------------------------------------------ ----------
Current Profile = G.PROFILE_LINEAR
10 = Radius 1
10 = Radius 2
165 = Height 1
90 = Height 2
1088 = Turns
22 = Wire Awg

--------------------------------------------- -------
Primary Coil Inputs:
------------------------------------------ ----------
Round Primary Conductor
12.7 = Radius 1
29.7 = Radius 2
90 = Height 1
90 = Height 2
11 = Turns
0.06 = Wire Diameter
0 = Ribbon Width
0 = Ribbon Thickness
0.14 = Primary Cap (uF) before 0.06 uf
0 = Total Lead Length
0 = Lead Diameter

---------------------------------------- ------------
Top Load Inputs:
------------------------------------------ ----------
Toroid #1: minor=20, major=80, height=180, topload

----------------------------------------- -----------
Secondary Outputs:
----------------------------------------- -----------
84.41 kHz = Secondary Resonant Frequency
90 deg ° = Angle of Secondary
75 cm = Length of Winding
14.51 cm = Turns Per Unit
0.04554 mm = Space Between Turns (edge to edge)
683.61 m = Length of Wire
3.75:1 = H/D Aspect Ratio
35.9105 Ohms = DC Resistance
34579 Ohms = Reactance at Resonance
1.978 kg = Weight of Wire
65.199 mH = Les-Effective Series Inductance
61.812 mH = Lee-Equivalent Energy Inductance
56.027 mH = Ldc-Low Frequency Inductance
54.527 pF = Ces-Effective Shunt Capacitance
57.515 pF = Cee-Equivalent Energy Capacitance
61.294 pF = Cdc-Low Frequency Capacitance
0.25 mm = Skin Depth
33.23 pF = Topload Effective Capacitance
99.9152 Ohms = Effective AC Resistance
346 = Q

----------------------------------------------- -----
Primary Outputs:
----------------------------------------- -----------
55.28 kHz = Primary Resonant Frequency
34.5 % high = Percent Detuned
0 deg ° = Angle of Primary
1465.24 cm = Length of Wire
893.42 mOhms = DC Resistance
1.485 cm = Average spacing between turns (edge to edge)
2.638 cm = Proximity between coils
2.16 cm = Recommended minimum proximity between coils
59.201 µH = Ldc-Low Frequency Inductance
0.06005 µF = Cap size needed with Primary L (reference)
0 µH = Lead Length Inductance
302.786 µH = Lm-Mutual Inductance
0.166 k = Coupling Coefficient
0.141 k = Recommended Coupling Coefficient
6.02 = Number of half cycles for energy transfer at K
53.54 µs = Time for total energy transfer (ideal quench time)

------------------------------------------- ---------


New spec

I launched auto-tune, and as expected, it will use fewer turns.

after it's very approximate, many things can change, I wait for my oscilloscope before measuring

J A V A T C version 13.2 - CONSOLIDATED OUTPUT
19/11/2017 à 12:25:29

Units = Centimeters
Ambient Temp = 68ºF

------------------------------------------- ---------
Surrounding Inputs:
------------------------------------------ ----------
2500 = Ground Plane Radius
2500 = Wall Radius
3800 = Ceiling Height

------------------------------------------ ----------
Secondary Coil Inputs:
------------------------------------------ ----------
Current Profile = G.PROFILE_LINEAR
10 = Radius 1
10 = Radius 2
165 = Height 1
90 = Height 2
1088 = Turns
22 = Wire Awg

--------------------------------------------- -------
Primary Coil Inputs:
------------------------------------------ ----------
Round Primary Conductor
12.7 = Radius 1
23.935 = Radius 2
90 = Height 1
90 = Height 2
7.2695 = Turns
0.06 = Wire Diameter
0 = Ribbon Width
0 = Ribbon Thickness
0.14 = Primary Cap (uF)
0 = Total Lead Length
0 = Lead Diameter

---------------------------------------- ------------
Top Load Inputs:
------------------------------------------ ----------
Toroid #1: minor=20, major=80, height=180, topload

----------------------------------------- -----------
Secondary Outputs:
----------------------------------------- -----------
84.41 kHz = Secondary Resonant Frequency
90 deg ° = Angle of Secondary
75 cm = Length of Winding
14.51 cm = Turns Per Unit
0.04554 mm = Space Between Turns (edge to edge)
683.61 m = Length of Wire
3.75:1 = H/D Aspect Ratio
35.9105 Ohms = DC Resistance
34579 Ohms = Reactance at Resonance
1.978 kg = Weight of Wire
65.199 mH = Les-Effective Series Inductance
61.812 mH = Lee-Equivalent Energy Inductance
56.027 mH = Ldc-Low Frequency Inductance
54.527 pF = Ces-Effective Shunt Capacitance
57.515 pF = Cee-Equivalent Energy Capacitance
61.294 pF = Cdc-Low Frequency Capacitance
0.25 mm = Skin Depth
33.23 pF = Topload Effective Capacitance
99.9152 Ohms = Effective AC Resistance
346 = Q




PS: I adjust the height of the machine, because I noticed that the secondary coil and the torus were too far

Re: my first personnal tesla coil
IamSmooth, Sun Nov 19 2017, 06:10PM


I so agree with that. I remember getting shocked for days every time I tried to move the secondary after disassembling the coil for storage. The static charge would just not go away.

Re: my first personnal tesla coil
paulj, Sun Dec 03 2017, 09:51AM

hello, some update.

The toroid is a real "problem nest" sanding is long is difficult, I do not think to get a perfect torus.
I do not recommend this technique for beginners, and for large toroid

For lack of space I tinkered the chassis to install the capacitors because they are larger than expected and bring them closer to the spark gap to limit the length of the cables.

Ps, I will repaint the chassis, otherwise it's not clean, I recall that the goal is to make a coil Tesla with the most material thrown in the trash.

Re: my first personnal tesla coil
paulj, Tue Dec 05 2017, 06:02AM




out of curiosity, I operated spark gap without primary capacitor, the result is beautiful.

Re: my first personnal tesla coil
paulj, Tue Mar 20 2018, 09:29AM

Hello

after a long absence, the Tesla Coil is finished and ready to be adjusted
the main problem encountered is toroid building,
to allow the adhesive tape to stick, I applied a coat of acrylic paint.

but the plaster layers have increased the diameter of the torus, so in theory the resonance frequency should be lower

so I decided not to cover the toroid completely with aluminum to compensate

why build a complicated torus?

because I wanted to limit the currents of foucaults (the separation visible to the right of the photo.

but, I think it's useless.

Re: my first personnal tesla coil
paulj, Mon Apr 02 2018, 11:50AM

so,

while waiting for the holidays (France), here are some details of safety. The control box is composed of:

-Protection against electrocutions.
Residual-current device, short circuit, overcurrent with circuit breaker
-remote control, the high power does not go into the buttons (it is mandatory) with several power contactors
-emergency stop with fall of the power circuit breaker.
-in the event of an emergency stop, a device prevents the coil tesla from restarting alone, with pushbuttons (no switch)
-A key (for emergency stop and control).
-finally, a sgtc specific device that prevents sending the high voltage if the rotating spark gap does not rotate.
-and indicator lights.

you can see the separation between the power unit (blue socket) and control (bakelite domino)

the gray box will contain the decoupling capacitors, and the high voltage filters for the network (for the moment, it contains only the capacitor of the fan, and the filter of spark gap.
























In the concept of the materials recovery, I didn't find crimping lugs for the primary, so I improvised with parts of aluminum.

for now that's all I can publish, I can't wait to start tunning

Re: my first personnal tesla coil
Sulaiman, Mon Apr 02 2018, 01:05PM


It may be useless - but it may not.

There should be a current induced in a torus topload, I'm sure that there is,
how significant this effect is on performance has not, to my knowledge, been investigated.
By having the opportunity to operate your topload with or without a complete electrical loop puts you in a unique position,
I'd be interested in the difference, especially if you could vary magnetic coupling by raising/lowering the topload relative to the secondary top turns.

Re: my first personnal tesla coil
paulj, Wed May 02 2018, 06:30AM

Hello, I'm stuck, I realize that my toroid is too heavy, and threatens to drop the coil in case of shaking.

I think use nylon straps to hold the secondary, but I do not know what material using, I'm thinking of nylon, what do you think?

Re: my first personnal tesla coil
teravolt, Thu May 03 2018, 04:24PM

I used flexible thermal ducting from the hardware store. its cheap and light

Re: my first personnal tesla coil
paulj, Thu May 17 2018, 10:33AM

Hello,

it's after three years of construction, I assembled the pieces, the toroid is crooked because of the unequal weight.

teravolt:
if there really is a problem, I will go on an flexible thermal

after a fast measurement, the resonant frequency of the secondary circuit turns around 120 khz, and 100 khz when the streamer touch the ground (nothing to do with the simulation of tesla Map)



I think to adjust the primary circuit so that there is a difference with the secondary cicuit of 20 khz

(not having a frequency meter, I use a 555 tuner and an oscilloscope)

my current will be limited to 16a during the tests.





ps: no test in my garage, I don't want fire

Re: my first personnal tesla coil
paulj, Sat May 19 2018, 11:00PM

first light !

I am a little disappointed, I was hoping for lightning 7 feet, mas they do not exceed 5.5 feet (this is my first personal design).
the power doesn't exceed 3900W, the frequency can't be probably found yet.

The setting looks very delicate, (shortening the primary coil by a few inches doubles the length of the streamers.)

I increased the coupling, and the height of the toroid.




PaulJ

Re: my first personnal tesla coil
paulj, Sat Aug 31 2019, 05:42AM

Hello,

I refresh my post after a year of absence.

I restarted my tesla coil after a 15 months of hibernation in order to use all its power by improving the power limited to 4kv, and here it is the disaster!

Two of my MOT transformers burn as a result of a current leak between the iron core and the secondary coil.
These MOT had no ground connection, so the high voltage was passed from the iron core to the coil.


So after repair, I measured the voltage of my MOT with a high voltage probe, I get between 3.9kv and 4kv at the output.

To obtain a doubled voltage, 8kv but rectified, I wish to have a double greinacher circuit with 2100 vac microwave capacitors.

what do you think of this installation?

I am looking for diodes able to withstand the required power (5kw) and high voltage returns in transformers.

What do you recommend ?

Paul

Re: my first personnal tesla coil
paulj, Sun Jan 03 2021, 06:07PM

Hello, My tesla coil now exceeds 2m of sparks to 80% of power, (more than double the secondary coil) but I had a serious problem, a spark formed between the primary and the secondary probably the earth not connected properly. ( on the left of the image)
The varnish is completely burnt but the wire has not melted, how can I fix it?

thanks in advance Paul.

Re: my first personnal tesla coil
paulj, Sun Jan 03 2021, 06:08PM

Hello, My tesla coil now exceeds 2m of sparks to 80% of power, (more than double the secondary coil) but I had a serious problem, a spark formed between the primary and the secondary probably the earth not connected properly. ( on the left of the image)
The varnish is completely burnt but the wire has not melted, how can I fix it?

thanks in advance Paul.
link of the fail video

Re: my first personnal tesla coil
Terry Fritz, Mon Jan 04 2021, 07:30AM

Hi Pail,

Clean the burned area up with alcohol and a toothbrush. Try to remove as much of the black stuff as possible. MAF sensor cleaner for cars is also pretty good and safe but test it on some wire and plastic first to be sure.



Sometimes you might have to pull off a turn or two and splice the wire ends together to be sure there are no shorts. It's also possible to rewind a small section if you really need to. Easier than rewinding the whole coil.

Then recoat the burned area with clear lacquer, nail polish, or other insulating paint that flows well.

A loss of ground or other loose connection can easily cause on arc like that.

Hope this helps.

Terry

BTW - Amazon has some pretty big rectifiers if you are still looking:

Re: my first personnal tesla coil
paulj, Mon Jan 04 2021, 02:22PM

hello, thank you for your answer, observing with a magnifying glass, the wire does not seem to be damaged, the high voltage has broken the many layers of polyurethane varnish, the resistance of the wire doesn't seem to have changed. there is too much varnish to remove the copper wire. I keep you informed.

Re: my first personnal tesla coil
paulj, Sat Jan 09 2021, 07:51PM

first big test, between 6,5 and 8,5 ft spark !!!!!