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Homemade HV transformer.

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Berni

Mon Dec 01 2008, 05:41PM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

Yes your schematic is something that might be worth looking in to. I will try to breadboard something when i have time.

The output voltage of this thing is not all the impressive. probably around 5-10kV peak when run at 300V.As i sead this transformer was just built to test out the concept and not in mind to make like 20kV. The current out of the thing was quite impressive tho since the arcs ware like those hot flaming arcs pulled off a MOT.I am going to improve the secondary a lot(more turns better isolation etc) From what i seen til now i can say its a great idea to try and make a HV transformer if you have a reasonably sized ferrite around.

However i don't think this is a good way of making huge voltages like 50kV and such, because its going to arcover all over the place.These things are more usable in the 5-20kV range, but the current out of them is great. I could see this power a quite well sized Tesla coil.

Will keep you updated on the progress.

EDIT:

I put together the protection circuit in switcher cad and it seams to work very well.It responds very fast to surges and the reset button works like a treat(It dosent override protection if held down)Now i need to assemble it for real

Also a pic of how my IGBT half bridge looks like with external diodes

1228163096 1132 FT1630 Safety Speed Test

rp181

Mon Dec 01 2008, 09:53PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

very neat. What chip are you using to control the gates of the IGBT (the alternating pulse one).

Berni

Mon Dec 01 2008, 10:05PM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

I use the L298 H bridge IC for driving a GDT with zener diodes on the output. As for the signal generation i simply use a 555 timer on roughly 50% duty.

Proud Mary

Mon Dec 01 2008, 10:31PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

With that power through-put, it could be a very good Cockcroft & Walton driver, even without trying to get a lot more voltage out of it than you have already.

Berni

Tue Dec 02 2008, 05:53AM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

But i don't have the HV diodes and caps to build one.

Backyard Skunkworks

Tue Dec 02 2008, 06:18AM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

Berni wrote ...

But i don't have the HV diodes and caps to build one.

has decent international shipping if I remember right. Mouser (or another supplier) will fill all your C-W needs.

Berni

Tue Dec 02 2008, 01:08PM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

For now im not realy that much interested in building a CV multiplier, meaby later.But i will proabobly full wave rectify the output (about 10 of 1,4kV diodes should make a nice diode for use in one) I seen on Steves website that half wave rectifying is not a very good idea for this kind of inverter.

I designed the board for the protection circuit but then i remembered i don't have a enable line on my gate driver. So now im modefiing it to have this feature. What should i do with the GDTs input to pull the gates of my IGBTs to 0V in a very short time. The easiest thing for me is to make the chip drive both sides of the GDT to low or high and so shorting it out, But that might resonate its series cap with it. Will this be a problem? So what is the best way?

jpsmith123

Tue Dec 02 2008, 03:24PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

How many turns are there in your secondary winding?

Berni

Tue Dec 02 2008, 05:17PM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

I estimate around 100

Steve Ward

Tue Dec 02 2008, 11:56PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Oh any i wonder how many W dose a typical flyback core handle?

*cringe*

Without getting deep into transformer design, you cant just stamp a power rating on a core. I will say that 500W is very optimistic given the tiny amount of copper on there. Perhaps 500W is realistic if you had even a 50% window fill of copper windings. Then again, for pulling arcs, where the load is low duty cycle, it may do 500W, and you just wont run it long enough to see it melt, or spontaneously combust :P.

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