neon HV transformer

Discussion in 'General Electronics Chat' started by ariemeir, Apr 19, 2013.

  1. ariemeir

    Thread Starter Member

    Jun 24, 2011
    68
    1
    Hi guys ,

    My question is about neon transformers.
    If i understand correctly, the older neon HV transformers were basically linear in the sense that they didn't change the frequency of the input signal and just multiplied it.

    The newer ones upshift the frequency into the high Khz range from the input 50/60 hz.

    I want to get a transformer of the old type and use it as a high voltage ac generator based on the output of my bipolar kepco (100w, 200v p2p) power supply (http://www.kepcopower.com/bop.htm)

    Basically i want to work around 50hz but for short periods i am hoping to run it in a higher frequency range : perhaps up to 1-2khz for a minute or so at a time (scientific experiments).


    I found this item on ebay, but i am not sure if it is old-school or a new type, i.e. what's the output frequency:
    http://www.ebay.com/itm/Luminous-tu...lianson-type-2229-cat-no-90FN30-/300852389836

    I went to allanson's website, and my intuition is that this is an old school
    transformer judging by the size and the weight of it, but i cannot be sure
    and don't want to waste 30$ on something i will not use.

    Perhaps someone could lend an experts advice ?

    If i feed 100v @ 50hz into this thing, will i get 9kv @ 50hz ?


    Kind regards,
    Lenny
     
  2. Brownout

    Well-Known Member

    Jan 10, 2012
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    998
    No transformers change the frequency. Newer "transformers" you're thinking are probably inverters. Inverters are more effieient, smaller and cheaper. If you find a 'real' transformer, it will work at line frequencies.
     
  3. tubeguy

    Well-Known Member

    Nov 3, 2012
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    The plate shows 120v:9kv or a ratio of 1:75
    So with 100v p in you would get about 7500v p out.
     
  4. ariemeir

    Thread Starter Member

    Jun 24, 2011
    68
    1
    Brownout, tubeguy, thanks for the prompt reply.

    I understand the statement "no transformer ever changes frequency"
    because this is how i learnt about transformers, but this item:

    http://www.ebay.com/itm/140924876514?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649


    claims to output 12kv, be a "transformer" (no word inverter mentioned)
    but the size is definitely smaller = less iron, so i suspect that it is an inverter
    really so it will push up my frequencies.


    Thank you for your answers.
    Lenny
     
  5. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Inverters "transform" the voltage, so they are often called transformers.

    The older types are the classic transformers, with a few windings on the primary side of the core and many windings on the secondary (to up the voltage). Newer NSTs are either inverters or switching supplies.

    The older types of NST DO NOT multiply the frequency. Output frequency is the same as the input frequency.
     
  6. ariemeir

    Thread Starter Member

    Jun 24, 2011
    68
    1
    thank you DerStrom8 !
     
  7. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,019
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    The description of that last link says it all "solid state transformer"

    It also warns that it is not for HV uses other than neon bulbs.
     
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  8. Brownout

    Well-Known Member

    Jan 10, 2012
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    That's probably a lawyer thing.
     
  9. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    I agree. I think it's mainly for idiots who might try to connect it to ordinary light bulbs. Sort of like the "WARNING: CONTENTS ARE HOT" on coffee cups at Dunkin Donuts (or was it McDonald's?). Some idiot was stupid and burned themselves, and sued the company.

    Now it's there for all the idiots who don't know coffee is hot :p

    I think that's what this warning is for. "WARNING: DO NOT USE ON ORDINARY LIGHT BULBS" :D
     
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  10. Georacer

    Moderator

    Nov 25, 2009
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    @Mikado
    Do not insert offtopic posts in threads with a specific direction.

    Offtopic posts were deleted.
     
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  11. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    @Brownout and DerStrom, it specifically mentions not for jacobs ladders or Tesla coils in the ad.
     
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  12. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    I would expect that's because the short circuit protection isn't designed for arcing over long periods of time. Overheating could be an issue as well.

    Thanks for pointing that out.

    Matt
     
  13. Brownout

    Well-Known Member

    Jan 10, 2012
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    I didn't see that in the ad. So, you're saying it's current rating is too low?
     
  14. DerStrom8

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    I don't think that low current is the problem, but when you have an arc it's effectively a short and draws full current. This will cause a lot of heating on the internal components and if there is any short circuit protection circuitry in there, it's probably not designed for constant shorts, maybe just a small spike here and there.
     
  15. Brownout

    Well-Known Member

    Jan 10, 2012
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    Well, for transformers, if the current rating is exceeded for a long time, you get heating. I know of no other parameter that would lead to over heating by simply applying an improper load. So if you're telling me that over heating would be a problem, then my response is the transformer is rated for too low current for maintaining an arc. If this is the case, then the OP can shop for one rated for higher current, or else figure out how long he can run this before giving it a rest.

    As an example of the latter, my welder has only a 50% duty cycle. If I run it for 10 minutes, I have to let it rest for 10 minutes.
     
  16. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Ah, okay. I was reading your post incorrectly. Yes, if the rating of the transformer is exceeded, that's what can cause excessive heat which can damage the internal components.

    I thought you were referring to the current output, which is different from the "current rating" of the internal components.
     
  17. Brownout

    Well-Known Member

    Jan 10, 2012
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    It's rated for 30mA. Here's a real old-school transformer. It's rated for 60mA, and the seller says it's prefect for HV projects. It's twice the cost, but twice the transformer. I might order this myself.

    Perhaps newer transformers have some safety features that make them unsuitable for HV projects, like current limiting. So, better to search for older ones, 80's vintage. BTW, HV is dangerous, and these old transformers can burn down your house. PLeeeeeeeese be careful!
     
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  18. Brownout

    Well-Known Member

    Jan 10, 2012
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  19. DerStrom8

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    The old-school transformers are the best. They're very rugged, almost impossible to damage, and can handle and supply a fair amount of current. They also don't get hot easily--the whole thing is usually potted in tar. I highly recommend them--I have three myself, found them indispensable when I was working on my Tesla coil. If you have the opportunity to get one, I recommend you do. They are definitely worth it!

    And I'm sure if you look around in the right places, you can get old scrap ones for next to nothing. You don't have to pay all that much. I happened to get all three of mine for free ;)

    The main reason you can't use newer transformers for Tesla coils is because they are a much higher frequency, and it's much more difficult to create a tank circuit to oscillate properly for the Tesla coil to function. As for jacob's ladders, as mentioned before, I expect that's because of the poor over-current protection.

    Brownout is right, this kind of voltage and current can kill you instantly if you touch it wrong, and the arcs can start fires, cause burns, etc. Be VERY CAREFUL when working with high voltage. Please keep checking back for advice if you have even the slightest doubt what you're doing. Ask the people who know the answers rather than taking unnecessary risks.

    Good luck!
    Matt
     
  20. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Forgot to mention, I suggest looking through your Yellow Pages for neon sign repair shops. They often have a bunch of these old ones lying around and they'll let them go for dirt cheap.
     
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