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Thread: 6 phase forked star secondary wound transformer

  1. #31
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    Quote Originally Posted by Jraef View Post
    I'm pretty sure saw it used once a long time ago as a way to have one large main transformer feeding multiple low voltage three and single phase loads to large IBM main frame computers (back in the day). Old IBM main frames used to use 415V 3 phase for the computer power supplies and 240V single phase for the fans and coolant pumps inside. So looking at those vectors, the large vectors would give you 2 sets of 3 phase 415V: a, c, e and f, b, d, then 3 connections for 240V single phase loads: h-n, g-n and i-n. I can imagine they did that for better balancing of the loads?

    The thing is, computers aren't built that way any more and those that were are museum pieces now, so it's highly unlikely that anyone uses this any longer. The only reason I saw it at all was because I helped scrap an old IBM mainframe computer from a hospital in the late 70s and that transformer was fascinating to me, so I looked it up. I never actually knew the voltages at the time, it was already apart when I saw it, but I learned years later that IBM had used 415V for the power, and I knew from that scrapping job that all the fans and pumps were 240V single phase, because we used them for different things, so I'm putting 2 and 2 together as to what was going on. Seeing this diagram now that I know more made me realize that's what I had seen.

    The transformer was I think around 150kVA, which if you think about the fact that my iPhone probably has as much computing power as that beast did back then, is pretty amazing. We stripped it for the copper, I think we got something like $25 for it at the time... We stripped out all the PC boards and sent them to a refiner, got back a little over 8 ounces of gold, but as I recall, we had just gone off of the gold standard a few years earlier and got something like $120/oz. Wish I had just kept it...
    Odd thing for an exam question though..........
    Si hoc legere scis nimium eruditionis habes.

  2. #32
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    Quote Originally Posted by Besoeker View Post
    Odd thing for an exam question though..........
    No argument from me on that, but I feel that sometimes people toss really oddball things into exams just to make sure nobody gets 100%...
    __________________________________________________ ____________________________
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  3. #33
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    Quote Originally Posted by Jraef View Post
    No argument from me on that, but I feel that sometimes people toss really oddball things into exams just to make sure nobody gets 100%...
    Yes, the 100% thing.
    That takes me back to a very long time ago.
    Mods be kind.
    I already got unreasonably admonished by a mod for saying I had 50 years experience despite that being the truth, but this was from an exam 54 years ago and it stuck in my mind.
    The question was about energy and I gave the correct numerical answer but I called it Joules. A
    ccording to the professor, should have been J. Rather like we label volts as V.
    My otherwise 100% was deducted by two points for that gross error of incompetence.
    My pal Al said the same thing you did. They don't want to give out 100% scores.
    Trivial, I know.

    And life moves on.
    It's now gone 07:00 here so I'll just walk the black and white brute for a few miles and observe the wonders of nature in spring.
    Last edited by Besoeker; 03-20-17 at 03:24 AM.
    Si hoc legere scis nimium eruditionis habes.

  4. #34
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    Quote Originally Posted by Besoeker View Post
    ...
    It's now gone 07:00 here so I'll just walk the black and white brute for a few miles and observe the wonders of nature in spring.
    "The flowers that bloom in the spring, tra la....."
    G&S

  5. #35
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    Years ago I went to PLC training at Allen Bradley in Milwaukee. On the final; exam, the last question was
    "Fill in the blank: The Allen Bradley Clock Tower contains the largest 4 faced clock in the ___________"
    No matter what answer you gave, they would mark it wrong for one of a dozen possible reasonings; if you said "The US", the answer was "No, in North America"; if you said "North America", they said "No, the world"; if you said "The world", they said "No, the solar system"; etc. etc. etc., meaning it's entire existence on the exam was so that nobody got 100%. Also if your co-workers clued you in before attending, they couldn't give you the correct answer in advance either. I hear they no longer do that simply because their clock is now only the largest 4 faced clock in North America, there are bigger ones elsewhere, even on this planet.
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  6. #36
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    Quote Originally Posted by GoldDigger View Post
    "The flowers that bloom in the spring, tra la....."
    G&S
    Takes me back to school days.............
    Si hoc legere scis nimium eruditionis habes.

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