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Thread: you're wrong. no you're stupid. well you're stupider so there.

  1. #51
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    Quote Originally Posted by topgone View Post
    These things here got me confused. Why do other people here claim that the setup is okay when the OP mentioned "it failed"? Did I miss a lot?
    failure not = burned up, damaged or over temp
    he was told the output was clamped at 840 kva, not possible
    it started and ran the motor fine
    he did not know how they ascertained that
    increase load gradually until output plateaued?
    we do know where the 840 was measured, makes a big difference
    filter takes 50-60 kva
    xfmr consumes 40 or so



  2. #52
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    Quote Originally Posted by Ingenieur View Post
    failure not = burned up, damaged or over temp
    he was told the output was clamped at 840 kva, not possible
    it started and ran the motor fine
    he did not know how they ascertained that
    increase load gradually until output plateaued?
    we do know where the 840 was measured, makes a big difference
    filter takes 50-60 kva
    xfmr consumes 40 or so
    For all you know, we have a similar setup that works fine in the plant. Our's is an 850kVA transformer driving a 665kW motor for a reciprocating pump! If you compare with the OP's setup, 875kVA for a 746kW (1,00hp) motor against our 850kVA for 665kW. The OPs setup is loading their transformer about 9.4 times greater than ours.

  3. #53
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    Quote Originally Posted by topgone View Post
    For all you know, we have a similar setup that works fine in the plant. Our's is an 850kVA transformer driving a 665kW motor for a reciprocating pump! If you compare with the OP's setup, 875kVA for a 746kW (1,00hp) motor against our 850kVA for 665kW. The OPs setup is loading their transformer about 9.4 times greater than ours.
    I am having trouble with that math! Your transformer to motor ratio is only slightly higher than the OP (1.17 vs 1.28).

    I dont think it ever went over temp. Here is what the OP said:

    . I've never seen it before, usually it just runs over temp.
    The way I read that, if you take into account the previous and next few sentences, he wasnt saying that his transformer went over temp. He was saying, in general overtemp is what he sees on an overloaded transformer versus the "current limit" phenomenon he thinks he is seeing now.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  4. #54
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    Quote Originally Posted by Fulthrotl View Post
    1HP = 746 watts.
    1,000 HP = 746,000 watts.

    that's not allowing for any losses whatsoever.
    no heat, transformer loss, zip.

    125% would be 932,500 watts.
    Agreed. The transformer simply isn't big enough regardless of any other problems that there may be.
    Si hoc legere scis nimium eruditionis habes.

  5. #55
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    Quote Originally Posted by Besoeker View Post
    An 875kVA transformer isn't big enough for a 1,000 hp motor. If you were in the business of designing drive systems you would have no difficulty in understanding that.
    There is no ad absurdum about it.
    The OP question is 840KVA limitation of 875KVA transformer. My proof is no evidence other than OP statement existed for it.

  6. #56
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    Quote Originally Posted by topgone View Post
    For all you know, we have a similar setup that works fine in the plant. Our's is an 850kVA transformer driving a 665kW motor for a reciprocating pump! If you compare with the OP's setup, 875kVA for a 746kW (1,00hp) motor against our 850kVA for 665kW. The OPs setup is loading their transformer about 9.4 times greater than ours.
    ???
    665/850 = 0.78
    746/875 = 0.85
    1.09 or 9% more
    moot
    when converted to kva for eff/pf for this motor range
    BOTH are ok
    Last edited by Ingenieur; 11-15-17 at 03:55 PM.



  7. #57
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    Quote Originally Posted by Fulthrotl View Post
    1HP = 746 watts.
    1,000 HP = 746,000 watts.

    that's not allowing for any losses whatsoever.
    no heat, transformer loss, zip.

    125% would be 932,500 watts.
    so?
    the xfmr is rated in mva
    the motor depending on measuring point
    is between 740-840 kva both < 875
    filter loss 60 kva
    xfmr 40 kva
    calcs http://forums.mikeholt.com/showthrea...52#post1871852

    drive mfgs (link previously posted) state xfmr kva >= motor kva
    which it is
    and the filter reduces stress on the xfmr

    no one can say the xfmr is too small
    the data indicates otherwise



  8. #58
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    Quote Originally Posted by Ingenieur View Post
    failure not = burned up, damaged or over temp
    From the OP:

    "usually it just runs over temp."

    I don't know why you continue to ignore that.
    Si hoc legere scis nimium eruditionis habes.

  9. #59
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    Quote Originally Posted by Besoeker View Post
    From the OP:

    "usually it just runs over temp."

    I don't know why you continue to ignore that.
    why do you misrepresent it?
    he said 'usually', but not in this case, in this case output was clamped at 840 kva
    impossible



  10. #60
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    Quote Originally Posted by electrofelon View Post
    ...
    I dont think it ever went over temp. Here is what the OP said:

    I've never seen it before, usually it just runs over temp.

    The way I read that, if you take into account the previous and next few sentences, he wasnt saying that his transformer went over temp. He was saying, in general overtemp is what he sees on an overloaded transformer versus the "current limit" phenomenon he thinks he is seeing now.
    I'm not the only one
    imo it was NOT over temp
    only output limited (impossible in this case)



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