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my schematic for dc resonant TC

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eniyuki

Sun Oct 18 2009, 07:30AM

Registered Member #2148 Joined: Tue Jun 02 2009, 02:22AM
Location:
Posts: 62

hi i made a schematic for my dc resonant tesla coil
i have 2 MOT rated 120v/2200v 1100 watts in series with voltage doubler.
i computed total output please correct if im wrong
2200+2200 = 4400v
4400*2 (voltage doubler) = 8800 VAC
8800*1.414 rectified = 12443 VDC
now im having a hard time computing for the output current of these mots.
can someone teach me how to calculate? iread a lot but couldnt find it.
can i use an ammeter to measure the output current across the HV output?
Untitled

Arcstarter

Sun Oct 18 2009, 03:46PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Nice, neat schematic.

How i would measure the current is by getting a 10 ohm resistor, and put it in parallel with the secondarys (warning, this will trip breakers, but it will show you the peak current). Then, read the voltage drop across the resistor. For every volt you measure across the 10 ohm resistor, you have 100ma.

I=E/R where I is current, E is voltage, and R is resistance...

Also, because of the charging choke, the tank cap will see around 2 times the voltage of the supply. Be sure your cap bank is rated for this. Also, you are charging with DC, but the tank cap will still see AC at whatever freq it resonates with the primary! For a single MOT and a doubler and plenty large reactor, my cap bank was 20Kv made with CDE, and i did not have any failures. Oddly.

teravolt

Sun Oct 18 2009, 03:52PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

your transformers can supply up to 1/2 amp on average and the amount of current your voltage multiplier can provide is going to be dependant on the size of C1-C4. Your multipier is a full wave cocroft walton voltage multiplier wich you may be able to look up. You know this also depends on how big a tesla you want to build. If I were doing this I would ground the center taps i.e. cases of transformers, get rid of D5, and put L2 on the negitive lead to balence the circuit.

Herr Zapp

Sun Oct 18 2009, 05:01PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

Eniyuki -

A few thoughts -

1. I'd use a variable-speed DC motor to drive your RSG, as this will allow you to vary the breakrate over a wide range. You'll see different characteristics to the streamers, and there will be different acoustic effects as the breakrate is varied.

2. I'd consider using groups of microwave oven capacitors in your voltage doubler, rather than a string of low-voltage electrolytic capacitors. The MO caps are designed to handle high ripple current, and have are designed to operate at about 3500 volts.

3. All the HV caps (C1 through C4) should have individual bleeder resistors as a safety precaution.

Regards,
Herr Zapp

Herr Zapp

Sun Oct 18 2009, 05:04PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

Teravolt -

Eniyuki's new circuit utilizes a DC resonant charging system.

In a DC resonant charging system, the "de-Q-ing" diode (D5) is absolutely essential.

The charging inductor L1 plus D5 are the key elements that charge the tank capacitor to twice the output voltage of the DC voltage doubler section.

See the comprehensive description of a DC Resonant Charging system on Richie Burnett's site:

Regards,
Herr Zapp

Steve Conner

Sun Oct 18 2009, 06:31PM

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

I'm to blame for the "strings of electrolytics" meme, because that's what I used on my Tesla-2. My reason for using them was just that I couldn't be bothered collecting a dozen MO caps. After all, part of the motivation of my original design was that it only needed one MOT!

Also, the polarities of most of your capacitors are backwards.

My power supply could put out a fair bit of current. I'm not sure exactly how much, but if the rotary gap power arced, the variac would make a big thump and the 13 amp fuse (at 240V) would blow. It also destroyed the current shunt resistor in the analog meter I was using to measure DC bus current.

I also used a variable speed motor: a brush motor pulled from an old vacuum cleaner, with speed control from a lamp dimmer that was sold as suitable for inductive loads.

Arcstarter

Sun Oct 18 2009, 11:16PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Not to mention, the lytics are much smaller than MO caps :P. That, and availability is why i chose to go by Conner's schematic and use the lytics.

I also use a universal motor, from a vacuum, and a light dimmer for speed control. I did a crazy 3krpm with that.

StevenCaton

Sun Oct 18 2009, 11:50PM

Registered Member #1845 Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211

How much more spark length are you guys getting with insanely high break rates, versus like a standard 240 bps.

teravolt

Mon Oct 19 2009, 12:10AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

thanks Herr Zapp, MOT's have the lo side of the transformers secondary connected to the case. Won't they arc or electricute with out a proper ground refrance. pehaps eniyuki if you made a supply that would be twice the current and half the voltage like this

teravolt

Mon Oct 19 2009, 12:11AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

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