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Signal generator output conversion to 2KV

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ragnar

Sun May 20 2007, 10:59AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
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Posts: 1425

Jeez guys, think about it. 2kV at 1MHz isn't that hard... but you'd want to be looking into a 5,000ohm load at least.

Peter, if it's any use:

1500V MOSFETs with low gate charge are available at Digikey. Search STW4N150.
With a 1kV power supply, you can get 2kV swing across the load with a fullbridge, leaving plenty of overhead for the devices.

I don't think 200W+ would be unreasonable with that kind of setup.

Energyman

Sun May 20 2007, 11:11AM

Registered Member #788 Joined: Sat May 19 2007, 02:31AM
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Hey bored chemist,

I said I have a basic knowledge of electronics - that's why I came here with full humility and asked the questions. If the numbers are silly, I am sure there is a work around to achieve what I need. If you can help educate me on the electronics that's great. If you want me to educate you about stuff that falls outside of this forum's scope, I would be happy to do a trade (off forum naturally). You also seem to be making an assumption that I have had no results already. If we were to remove all the stuff from our lives that resulted from the tinkering of the mad scientists life would be very different. But I justify..... and I only came here seeking knowledge!

mikeselectricstuff

Sun May 20 2007, 09:01PM

Registered Member #311 Joined: Sun Mar 12 2006, 08:28PM
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Posts: 253

A major problem with HV at high frequency is capacitance - you don't need many pf to present a substantial load.

ShawnLG

Mon May 21 2007, 02:01AM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
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"1500V MOSFETs with low gate charge are available at Digikey. Search STW4N150.
With a 1kV power supply, you can get 2kV swing across the load with a fullbridge, leaving plenty of overhead for the devices."

Those fets have a source to drain capacitance of 120pf. Switching 1kv at 1Mhz would dissipate 60 watts of power! High voltage transistors may be better for this application.

HV Enthusiast

Mon May 21 2007, 02:53AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

As Bored Chemist said, you are going to need a pretty damn advanced system to reproduce a square wave at 2kV and 1MHz. You're not going to be able to get the square wave with a conventional full-bridge using standard isolation gate transformers. You'll need to use a direct drive to get the rise-times necessary such as a cascode arrangement.

Sine wave would be easy, but here you'll be running the MOSFETs in their linear region and dissipate lots and lots of heat.

I like what Steve said - go with some tubes.

Remember, the old adage still holds true. With solid state devices, current is free and with tube devices, voltage is free.

Steve Conner

Mon May 21 2007, 08:55AM

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

I think you'll be on a road to nowhere if you try and argue that a square wave generates scalar waves any better than whatever other shape of wave, since the scientific community doesn't even accept that scalar waves exist in the first place. We certainly don't accept that they exist, and we have a board policy of merciless censorship of anyone who tries to persuade us otherwise.

But anyway, let's take a look at what happens when you apply high voltages to a coil.

If you put 2kV from a low impedance MOSFET driver onto a caduceus coil with a resistance of 10 ohms, well, a caduceus coil has no inductance, so there's not a lot to limit the current. You won't quite get the 200 amps that Ohm's law would suggest because of stray inductance, but it won't be far off. I expect the magic smoke would come out of your MOSFETs in about 5 milliseconds.

Hence why I recommended using tubes, as they're quite hard to destroy, have a naturally high impedance to limit the current draw, and the grid of a tetrode is easy to drive. Tetrode tubes are current sources: If you apply a square wave to the grid, the tube will try to put a square wave of current through the load, and the load will develop whatever voltage it wants.

I heard some of the audiophile 300Bs even have orgone in them.

Energyman

Mon May 21 2007, 10:16AM

Registered Member #788 Joined: Sat May 19 2007, 02:31AM
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Posts: 10

Lots of lively debate on this one. I should have done more research before I mentioned what I wanted this for on this forum (assumed you had embraced all of Tesla's work). But now I am not the one mentioning orgone!

So, purely on the electronics. Is it the concensus that valves might offer the best solution? Would it help to increase the resistance of the coil by replacing it with resistance wire? I have done a little research and it seems I might be able to get it up to about 100K on about 20m (60') of wire which is what I have now.

Steve Conner

Mon May 21 2007, 11:30AM

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

We have embraced all of Tesla's work, well all of it that can be proven to exist anyway. Why not go and read our wiki

and Paul Nicholson's paper on non-Hertzian waves

I'm not asking you to believe this, just stating that it is what we believe, and you won't change our minds.

Again, you can make the coil out of whatever you want. A decent sized valve won't really care what load you present to it, it will just dissipate as heat whatever power it didn't manage to deliver to the load. So just pick a good big valve and cool it with a blower.

Making the coil out of resistance wire may make it an easier load to drive, but it won't actually cause it to radiate better as an antenna. Well, that is how it works in conventional physics at least! As far as the unconventional aspects of your experiment go, you're on your own...

Bored Chemist

Mon May 21 2007, 05:47PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Energyman, with or without humility doesn't matter. You asked a question in your first post about feeding a roughly 1MHz square wave of 2KV amplitude into a 10 ohm coil.
I pointed out that the idea of doing that without a huge budget is silly.
People have sugested using valves; this won't actually get the result you specified unless they are capable of delivering the thick end of a million watts of power. The only advantage to valves is that, while they won't work, they might not die trying.
Unless you are going to tell me that this thing cures cancer, ends world poverty and makes a really good cup of tea I can't help wondering how it can have any benfit that would excede its enormous cost.
I gather that you can get lots of valves on the surplus market
Would someone who knows more about it than me (that's most of you) care to estimate the cost of the valves etc. needed to build this massive transmitter?
You will also need a big power supply. You could ask your local supplier to set you up with a couple of MW worth of connection but, unless you want to watch them laugh themselves sick, I wouldn't bother. What you need is one of these

The "buy it now" price is more than my house cost but I'm sure that won't be a problem. OK, it will be a problem but probably less of one than cooling the coil you put it into.

Steve Conner

Mon May 21 2007, 09:13PM

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

BC, what does it matter? Of course nothing we suggest will deliver a million watts, but this guy doesn't believe in the laws of physics, so I thought we may as well humour him and give him something to play with. He probably never realised that the 2kV and 10 ohm figures implied the need for 400,000 watts of power anyway.

Anyway, what if it were 10 ohms of reactance with negligible resistance? Reactance doesn't dissipate power.

What if he only wanted pulsed power and not continuous? A 400kW pulse at 1.5MHz isn't beyond the reach of a determined hobbyist (though my record is only 50kW at 220kHz)

And who's to say you need 400,000 watts to make scalar waves anyway? They don't exist, so 400 watts will fail to make them just as spectacularly as 400kW would.

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