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torroidal transformer vendor

Discussion in 'Electronic Design' started by John Larkin, Feb 8, 2005.

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  1. John Larkin

    John Larkin Guest


    Can anybody recommend a good source for a custom torroidal power
    transformer? It will be roughly 50 VA; we need prototypes fast, and
    maybe 100 per year after that.

    There are about 200 suppliers listed in the EEM for torroids, and I
    guess we'll spam lots of them with our spec, but I just wondered if
    anybody has a vendor they especially like.


  2. Hey John,
    Rayco Electronics, lightning free prototypes, great production prices,
    works for me.
  3. John Larkin

    John Larkin Guest

    Thanks! We'll zap them our spec.

  4. I've used their standard products in that range:

    You know this, but toroidal power xfmrs can have a nasty turn-on
    current surge.

    Best regards,
    Spehro Pefhany
  5. John Larkin

    John Larkin Guest

    Thanks; we'll try them. And yeah, we had to go to TT superslow fuzes
    for this one. We also used the inrush limiter thingies, the ones that
    look like black disc caps. Primary resistance runs about 5 ohms per
    120 winding, 2.5 or so in parallel, so it's not all that bad, 50 amps
    without the thermistor gadgets. But our existing transformer vendor
    mucked the design and they saturate at 50 Hz, so we're blowing fuzes
    in Europe. These are megabuck systems and our customer is not happy.

  6. Joerg

    Joerg Guest

    Hello John,

    I had lots of good experience with Ulveco. There have been mergers et
    cetera and I believe in the US it might now be:

    Regards, Joerg
  7. John Larkin

    John Larkin Guest

    Thanks. We'll add them to the bid list.

    I hate magnetics.

  8. Joerg

    Joerg Guest

    Hello John,
    Power transformers can be kind of boring. But I love ferrite stuff. You
    can do cool things with those.

    Regards, Joerg
  9. John Larkin

    John Larkin Guest

    I do like transmission-line transformers wound with micro-coax. We
    just did a small 1:1 that puts a 60 volt pulse into 50 ohms with
    rise/fall around 2 ns. That's fun.

  10. Paul Mathews

    Paul Mathews Guest

    You'll get farther with your searching if you spell it 'toroid', with
    one R.

    If you're serious about wanting production pricing, I suggest you
    contact Bridgeport/Alphacore/Tortran (all the same company, really)

    Piece prices from them are often much lower than the competition.
    Quality is good.

    If you're concerned about turn-on surges, look for an article about new
    toroid transformers designed to limit power-on surge:

    Paul Mathews
  11. John Larkin

    John Larkin Guest

    No problem photocopying the page out of the EEM and giving it to
    purchasing. It must have 200 vendors.
    As I told Speff, we have NTC surge limiters and TT fuzes, so that
    seems to be under control.

  12. legg

    legg Guest

    Your own spotty behind was covered by the mention of 50Hz, somewhere
    in the spec?

    Don't you test these things?

  13. Pooh Bear

    Pooh Bear Guest

    Toroid International.

    The MD owns the company and is highly knowledgable and most helpful.
    Their prices are good too as they manufacture in asia.

  14. John Larkin

    John Larkin Guest

    Sure. At 10% overvoltage.
    The guy who spec'd and tested the trannies no longer works for me; one
    day he walked into my office, said "it's time to move on" and left.
    Interestingly, he used to work for Signal Transformer. I guess he
    didn't test it for saturation. All you really need to do is
    overvoltage it at 60 Hz, find the knee, and multiply by 5/6.

    Our customer (it's an OEM product) took our gadget to a major test lab
    for the full CE suite, including specific transformer tests. Their
    test report *justifies* why it was not necessary to actually test at
    50 Hz. There's lots of blame to go around.

  15. Pooh Bear

    Pooh Bear Guest

    You didn't put 50Hz on the spec ?

    Sounds like a transformer supplier who doesn't understand that there's a
    whole world out there.

    Oh - and if you're selling in Europe don't forget to use IEC spec fuses
    not UL. The blowing characteristics are very different too.

    I've *never* had to use a TT fuse. Ts normally work just fine for me and
    I regularly use toroids.

    Fuse only needs to blow when ( typically ) you short out any one of the
    secondary side reservoir caps btw.

  16. John Larkin

    John Larkin Guest

    Of course we did.
    We're using TT fuses.
    The CE test involves loading the transformer secondary to just below
    the fuse blow point and then waiting to see how hot the transformer
    gets; that is a lot nastier than a clean short. And this box has no
    fans. So we have to use the smallest possible fuse rating, or we pay
    for it in transformer iron. So between the powerup surges (core+caps)
    and the fact that this is a pulsed power amp, things get interesting.

    I think what happened was that the original transformer design was OK
    but a bit too big. Somebody at the transformer company (another
    somebody "no longer here") scrunched the design program and wound up
    with a transformer that was smaller but had no saturation margin.

  17. There used to be a UK contributor to sed (Mark
    Daniels) who owns his own transformer company.
    I bought some custom transformers from him a
    couple of years ago. They were ok.

    Jem Electronics,
    173a High Street,
    Clay Cross,
    S45 9DZ,
    0870 787 1708.


    BTW: What's the rough spec?
    PCB-mount or flying leads?
    Secondary Volts/Amps?

    Note that Soddes Law says that urgently trying to
    get a new transformer designed and wound, by an
    unknown supplier, in a different country, could bite
    you in the bum.
  18. I read in that John Larkin <[email protected]
    landPLEASEtechnology.XXX> wrote (in <[email protected]>) about 'torroidal transformer vendor', on Tue, 8 Feb 2005:
    Which standard are you applying? It sounds to me that you may not be
    applying the correct one.
  19. I read in that Paul Mathews>) about 'torroidal transformer vendor', on Tue, 8 Feb
    Do you have the title of the article? I couldn't find it on the site.
  20. Pooh Bear

    Pooh Bear Guest

    This sounds very wrong. IEC regs simply apply component failure simulations
    to test such stuff.

    I think someone's misadvising you re: the CE safety test btw.

    I have considerable experience of both safety and EMC CE approvals.

    Is it a US lab that thinks you have to test that way ?

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