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large VTTC project questions

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Kolas

Tue Mar 28 2006, 05:23AM

Registered Member #102 Joined: Thu Feb 09 2006, 08:15PM
Location: Raleigh, NC
Posts: 169

Hi guys, this is a rather complex project I'm taking on,
and I have a few questions
I'm planning on using the 6696A for my triode.
I have wound a dual secondary plate transformer that will supply aproximatly 7kV at around 2A.

I am deeply concerned about RF leakage into the mians power. ( I have pretty important computers on the same grid)
So my first question is. how can I be sure too protect my computers from accedental RF back wash. I have been told, in the past, that the high frequency that i will be using 2-20MHz will be swallowed in the large plate transformer's core. But im still worried.

A few attempts to rectify this problem (heh) would be:
(1)use a low pass filter, but problems present them selves quite quickly. where would i get such a large low pass filter? (14kW)
(2) Use a half bridge to drive the plate transformer at 60hz, this would efectivly isolate the mains power from any tank oscialltions due to the extreamly large filter capacitor that would be needed to efectilvy smooth rectified mains at 14kW. (single phase)
(3) This is the last option that has presented it's self. use a generator to supply needed current. This option would likely involve using a half bridge to simulate 60Hz anyway, as the only attainable motor large enouph would be a 3 phase motor. (easily rectified, and smooothed)

Anyway the same question goes for the filliment transfomer, would the tank RF be able to leak back into the mains power this way?

Well, I apreciate the attention of anyone who bothered to read all that above. And I would gladly read any long winded responses.
I'll wait a few days before bringing up the grid drive topology heh.

Kolas

Conundrum

Tue Mar 28 2006, 05:34PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

I've seen some pretty large filters in PC power supplies- 14kW might be a bit too high but you can probably copy the basic design .

-A

"Bother" said Pooh, as he tore a hole in the fabric of space-time...

Nik

Tue Mar 28 2006, 07:07PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

I'm not sure but you could probably parrallel several off the shelf filters. I have found 1kw filters in micorwves and photo copiers and it would probably not be to hard to get 14 or them from ebay or the like.

Hazmatt_(The Underdog)

Tue Mar 28 2006, 07:34PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

From the computer standpoint I've noticed a lot of reports of fried network components.
So what I would do before a run is unplug the computer and router. Other then that all you have to worry about is you yourself touching something that's grounded and getting a nasty burn, or touching the computer and zapping it in a similar fashion.

Kolas

Wed Mar 29 2006, 02:25AM

Registered Member #102 Joined: Thu Feb 09 2006, 08:15PM
Location: Raleigh, NC
Posts: 169

yes i soppse, but the computers realyl shoudnt be goign offline
that's the point :(

kolas

teravolt

Wed Mar 29 2006, 05:42AM

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

You won't have to worry about RF in the power lines much because the thransformers will act like filters. But if your still are concerned use some series inductance with your plate transformers as a choke. The moast I think you may have to worry about is radiated RF enegy. Lots of equipment have there own shielding and won't be afectid unless you fire it up in the same room. Good luck N.B.

Steve Conner

Wed Mar 29 2006, 10:47AM

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

The primary circuit can (and should) be fitted with bypass capacitors to stop RF feeding back into the plate transformer. Differential mode RF (such as you would get from a lack of bypassing) will more likely just fry the transformer than feed back into the mains. Common-mode RF will feed back into the mains through the transformer's inter-winding capacitance, but the coil shouldn't generate much of that.

However, even if you got all that stuff sorted, a lot of RF will still radiate from the coil and topload, and conduct through the RF ground connection. 14kW of RF will get into everything in your house. Ideally you should enclose the whole apparatus in a faraday cage and any wires passing into the cage have to have EMI filters on them. If you can't afford or be bothered doing that, better shut down your computers and disconnect them from the power and network cables.

GimpyJoe

Wed Mar 29 2006, 02:40PM

Registered Member #316 Joined: Mon Mar 13 2006, 01:30PM
Location: Marietta, GA
Posts: 212

Don't forget about the home security system either. Last night I was running my small 811a vttc in my room and the fire alarm turned on. This has also happened with my 200w sgtc.

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