Re: Is this transformer good for tesla power supply? + some TC desing
Andrew L., Thu Mar 22 2007, 09:10PM

Wooow where did you get that "pig".
I would say that it is pretty good for a medium/large tesla coil.
It would be good if you could have it submerged in oil when you are using it.

Re: Is this transformer good for tesla power supply? + some TC desing
Sulaiman, Thu Mar 22 2007, 09:21PM

I think it would be good
BUT

-it's not like an NST or MOT, it has no inherent current-limiting
so I guess the best would be to use dc resonant-charging with a rotary spark gap,
maybe with a voltage multiplier ?

Re: Is this transformer good for tesla power supply? + some TC desing
Marko, Thu Mar 22 2007, 09:50PM

Yes, as voltage is a bit low considering it's power, and you need a big current limiting inductor anyway, resonant charging may be good.

Re: Is this transformer good for tesla power supply? + some TC desing
Kizmo, Thu Mar 22 2007, 11:17PM

Yes, secondary voltage is a bit low. This is my 1st tesla and im allready planned to use resonant charging with rotary spark gap. At least i got fat arcs with that power :D

Is there simple way to make that voltage doubler mentioned earlier, does something like this work:

http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/ietron2/voldoub.gif

Re: Is this transformer good for tesla power supply? + some TC desing
Sulaiman, Fri Mar 23 2007, 12:26AM

Yes, just like that.

It should give you about 15 kV dc.
With resonant charging you'll be up near 30 kV so smooth surfaces to reduce corona will be required.

Re: Is this transformer good for tesla power supply? + some TC desing
sparky, Fri Mar 23 2007, 01:51AM

Oh nice trannie!! Yeah, I'd be wanting to make a high powered DC power supply out of this unit. I bet on small runs you could easily push the transformer to 4kVA@15 kVDC without significant heating what so ever...

YOU MUST PUT THIS TRANSFORMER UNDER OIL!!! Its a must!!!

Re: Is this transformer good for tesla power supply? + some TC desing
Kizmo, Fri Mar 23 2007, 03:48AM

So under oil it goes :)

(have to make aluminum countainer, put tranny in there and fill it up with transformer oil. Countainer will be grounded naturally)

Re: Is this transformer good for tesla power supply? + some TC desing
Coronafix, Fri Mar 23 2007, 04:47AM

I'd just put it up on some spacers in a plastic container under oil.
You can still ground it.
I don't think you'll get much heat coming off of it.

Re: Is this transformer good for tesla power supply? + some TC desing
Marko, Fri Mar 23 2007, 12:29PM

If the transformer wasn't designed to be run exclusively under oil, I wouldn't say it's an apsolute must considering it won't run 24hrs a day for weeks.

But it surely wouldn't be any bad, so put it under oil if you don't consider it too messy.

Re: Is this transformer good for tesla power supply? + some TC desing
Kizmo, Sat Mar 24 2007, 02:17AM

Well, i did some 'plans' with paint, could someone tell me if this circuit has something that should be altered. I have allso 'few' questions :)

Here is the powersupply:

http://img87.imageshack.us/img87/6750/powersupplyoi0.png

This part is pretty clear, im planning to use stack of 1N4007:s in voltage doubler because they are cheap. How big capacitors i should use? Do i need extra filter cap for 15kVDC line?

And here is rest of the coil:

http://img87.imageshack.us/img87/1440/resttz0.png

De-Qing diode will be allso stack of 1N4007 diodes in series. Charging reactor (inductor) cant be found anywhere so i have to make my own, does air-core inductor work? Any suggestions for values? Capacitor tank will be MMC stack (if i understood correctly, its best to make Primary/secondary coil first and then calculate values for cap tank?)

Re: Is this transformer good for tesla power supply? + some TC desing
Sulaiman, Sat Mar 24 2007, 10:31AM

The charging inductor should be air- of ferrite-cored and as large as possible
(to reduce the peak charging current)
with the limit of;

The charging voltage across the capacitor approximates to half a cycle of a sinewave
(more like a negative cosine wave)
so Ldc < 1 / (Cp x PI x PI x BPS x BPS)

e.g. If BPS = 200 and Cp = 22nF then Ldc < 115 Henries !

So there's not much chance you'll inadvertantly exceed that value with an air-cored inductor.

Re: Is this transformer good for tesla power supply? + some TC desing
Kizmo, Sat Mar 24 2007, 01:40PM

Yep, have to crunch some numbers.

Re: Is this transformer good for tesla power supply? + some TC desing
Marko, Sat Mar 24 2007, 02:52PM


I just don't wan't misconceptions to be spread: charging reactor by any means *should not* be air cored because it would, obivously, require an insane amount of windings to compensate this. 115H air cored inductor? That would probably be bigger than entire coil.

Since it operates on relatively low frequency using an iron core is compeltely fine.
A secondary of a mot is generally a favourite, but there are number of ways they are made.


Also, something tells me that this figure of 115H inductor can't be right. It should be few to few tens of henries for coil of that size.


I guess you chould best look at richie burnett's site, It's still maybe the best info ever!

Re: Is this transformer good for tesla power supply? + some TC desing
Kizmo, Sat Mar 24 2007, 04:40PM

Yep, that would be huge :D

Fortunately i have few MOT's around so charging inductor problem is solved. I bought 60x Cornell-Dubillier 942C20P15K-F caps from ebay for Cap tank (15 in series and 4 of those stacs in parallel, should give about 37.5nF @ 30kV).

Re: Is this transformer good for tesla power supply? + some TC desing
Kizmo, Tue Apr 03 2007, 06:43PM

Hi!

I just tested my transformer, played with arcs for a while and it seems to be working well. (that wrench started glow red and tranny didn't even get warm)
link:

Now im working with voltage doubler, how big capacitors i should use in this circuit?
link:


AND the filter cap for final DC output (~15kVDC), some say its necessary and others say its not needed?