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1st timer with Tesla Coils (coil kicks ass)

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sparky

Sun Aug 26 2007, 12:30AM

Registered Member #530 Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178

bleeder resistors aren't really needed... I don't use them nor have I used them in all my Tesla coils built to date. I find there is very little residual charge left over in my caps after use.

Kizmo

Tue Aug 28 2007, 07:56PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Still waiting 4mm tungsten rods for RSG

MMC half way done, i ran out of zip ties (2 of these boards will be made). MMC base plate is cheap cutting board and caps are secured by zip ties.

sparky

Tue Aug 28 2007, 08:22PM

Registered Member #530 Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178

Beautiful construction Kizmo! I enjoy your simplistic design on those caps...I'm not sure but value of CDE caps are those?

what voltage rating @ what uF value??

Kizmo

Tue Aug 28 2007, 08:46PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Those capacitors are the proven thing for TC usage, 72pcs of Cornell Dubilier 942C20P15K-F 150nF/2kV. That makes 37.5nF @ 24kV / cutting board

Kizmo

Fri Aug 31 2007, 10:14PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

I dont know what to say right now, im so excited! I just fired up my first tesla coil and it was success. I did small test with static spark gap because my coil was ready besides i didn't got tungsten rods for my ARSG. I quickly put together one from few peaces of wood, two strong blots and airgun for quenching.

I got only minor problems:
- I got 2 primary-secondary strikes because of wrong coupling. (two holes burned to secondary coils varnish, fixed with epoxy and plastic sheets. Needs to be fixed better later)
- and my installations cough on fire few times (at least i learned where not to put just tape!)

Here is longest discharge so far:

And here is small video:

Now i need to take that coil apart and figure out way to repair those burned pinholes from secondary. And of course make that rotary spark gap :)

Steve Conner

Sat Sept 01 2007, 09:27AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Wow, looking good.

Kizmo

Sun Sept 02 2007, 09:19PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

I did some tests with static gap. I got longest discharge about 60" to grounded metal pole. Power draw is now between 4-5kW so it SHOULD do better than that?

Here is my setup:
- MOT 4-pack ballasted around 4-5kW. Output voltage is slightly over 7kV (measured)
- 75nF / 24kV tank cap
- 1237 turns in secondary (86mH)
- 12 turns in primary, tapped at 9th turn. (0.054mH)
- Static spark gap, two electrodes made out of 12mm steel bolts. Quenching and cooling is done by airgun. Air moves very quickly between bolts (full blast)

Could 'bad' performance be caused by one of these reasons:

- Static gap just cant handle power (bolts will get glowing red after 10 minutes of operation and airflow throws away molten metal)
- Im still badly out of tune
- Input voltage is too low for proper spark gap action

Steve Conner

Mon Sept 03 2007, 10:44AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Hi Kizmo,

Your setup is probably running at a high break rate due to the static gap and fairly small tank capacitor compared to the power supply.

The 1.7* sqrt(power) thing only holds for coils operating at 120 breaks per second: higher break rates give less efficiency, because they mainly just make the sparks brighter and hotter, rather than lengthening them.

Kizmo

Mon Sept 03 2007, 01:08PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Okay, so RSG will make difference :)

Kizmo

Mon Sept 17 2007, 05:39PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

I decided to extend my MOT stack to full 8-pack. As base i will use the old 4-pack and another four mots are submerged in detergent-free mineral motor oil. Outer 2 mots are modified so that i disconnected HV winging from transformer core to decrease risk of secondary-core-primary flashover.

Here is pic about 'new' MOT's under the oil (none of those are cheap made in china MOT's, only 2x Samsung and 2x AEG):

original 4-pack is connected to 'LV' wires and HV output comes from 'HV' wires. I heated up the oil to make it as thin as possible to get air bubbles out. Case is metal (old car petrol tank) and it is carefully grounded from 3 different spot (i don't want that someone get shocked dies if insulation between HV wires and casing somehow fails)

Tomorrow we will see if this ends with nice & smoothly running transformer stack or total disaster and possible fire because of under-oil power arcing. Maybe its good to bring big fire extinguisher with me :)

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