oh the joys of craigslist/the NST jackpot/lookie what I got!!

[chad ramey]

So I was craigslisting today and I came upon a guy trying to sell 21 neon sign transformers. I drove an hour and a half to go look at them and ended up buying them. They are varying voltages ranging from 7kv to 15.5kv. Any ideas on how they should be applied to my fusor?

p.s. I'm trying to use them as my primary power source
(as a side note, I would like to add that I have read several papers on NST rectification and how the transformers should be used, I posted this just for opinions, hoping to hear something new)
Thanks,
Chad

[David D Speck MD]

They look like pretty transformers -- pretty much new looking. Regrettably, previous postings have indicated the unsuitability of NSTs for all but demo fusors -- they just don't go to high enough voltages.

Perhaps you can eBay them to Tesla Coil builders and use the proceeds to buy a good Spellman. If you have any 15 kV @ 60 mA NST units, I'd be interested!

Dave

[chad ramey]

Thats pretty much what I've learned from my research so far but I figured it wouldn't hurt to ask for input. I think what I'm going to do is use them for plasma testing and then like you said, sell them to buy a legit power supply such as a glassman or spellman.

I'll check tomorrow and let you know.

Thanks for your input,
Chad

[Chris Bradley]

If you think you know what you're doing, and have matching transformers in your set, you could study http://www.kronjaeger.com/hv/hv/src/obit/index.html and see if you want to try this. Bear in mind that this leaves the casings of the transformers live to HV so only contemplate it if you're very comfortable with electrical engineering and also build them all into a well-insulated enclosure.

[AllenWallace]

I don't totally agree that NST are only usable for demo fusors. I have often speculated that if you had enough NST in parallel, the combined current would be useful for a neutron generation.

I'd connect each transformer using a full wave rectifier (two diodes scavenged from discarded microwave ovens) and connecting the DC all in parallel. This way you can mix and match the different transformer voltages.

As I recall, a NST was current limited to a few hundred volts in a fusor, but with 21 of these babies in parallel, it's possible that the voltage count jump to 2 few KV.

[chad ramey]

I really appreciate your thoughts on the topic, I was thinking much the same thing and was kind of wondering why every one else was so quick to shoot the idea of using NSTs for more than demo fusors. I am working with a few electrical engineers so I'll run the idea by them and see what they say and post my findings on here.

Thanks,
Chad

[Chris Bradley]

Wallace, Allen wrote:
> I'd connect each transformer using a full wave rectifier (two diodes scavenged from discarded microwave ovens) and connecting the DC all in parallel. This way you can mix and match the different transformer voltages.

Just remeber that you *MUST NOT* connect them in series.

NST transformers are not designed to be isolated between the suppy and the centre tap to the peak secondary voltages.

In this case, the centre tap (thus the case) of the 'pushed up' transformers will become live to the HV potential. As they do so, they will likely short across to the primaries, down the mains lead connected to that transformer, back up the one closest to ground potential, thus completing the circuit via your domestic supply.

Connecting in parallel has other hidden risks of mis-phasing and presumably mis-matched voltages that might work against each other. I am not sure how that is affected when you put rectifiers in the way.

The only way I think is safe is as shown on Jochen's web page, and you need to make sure they are balanced transformers.