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  1. #1
    Join Date
    Jul 2009
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    What is the code on the max voltage imbalance for running a three phase motor

    I cant find the % anywhere. I was thinking it was 5% but not sure

  2. #2
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    Aug 2012
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    3% back when I was in school, 00-04, I think 4% max now is standard

    Sent from my SCH-I500 using Tapatalk 2

  3. #3
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    Quote Originally Posted by ReferYankee View Post
    3% back when I was in school, 00-04, I think 4% max now is standard

    Sent from my SCH-I500 using Tapatalk 2
    How about the starting current drawn by a single phase motor how much can that exceed running current Is it 2 to 3 times or 7 to 9

  4. #4
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    Aug 2007
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    Northern VA 38 degrees N by 76 degrees W
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    Quote Originally Posted by bwd111 View Post
    I cant find the % anywhere. I was thinking it was 5% but not sure
    Not a code but a NEMA standard 2%

  5. #5
    Join Date
    Oct 2012
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    Los Angeles, CA, USA
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    2% max voltage imbalance and I believe inrush is 5-8 times the normal running amps

  6. #6
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    Dec 2012
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    Here is another good thread on the subject. http://hvac-talk.com/vbb/showthread....amp;p=15366761

  7. #7
    Join Date
    May 2010
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    Canada
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    They are teaching us 2% voltage and 10% amperage in school as good practice ( not sure about code )

  8. #8
    Join Date
    Dec 2012
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    columbus, OH
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    Quote Originally Posted by eddiegoodfellar View Post
    They are teaching us 2% voltage and 10% amperage in school as good practice ( not sure about code )
    You have an NCCER curriculum at your school?

  9. #9
    Join Date
    Jun 2013
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    Quote Originally Posted by bwd111 View Post
    I cant find the % anywhere. I was thinking it was 5% but not sure
    Never really thought about it . You kind of lived with what the power company gave you . Unless it was TOO bad & the power company found something was defective .

    Best I remember , you can get a pretty large imbalance on open delta 3 phase 240 VAC ?

    Do some of the rural power companies still use open delta ?

    I have also seen 240 VAC run 255 VAC . 480 VAC at 500 VAC fairly common .

    God bless
    Wyr

  10. #10
    Join Date
    Dec 2004
    Location
    maple ridge, bc
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    In Canada the maximum deviation from averaged voltage in 3 phase circuits is 2%. Not sure what single phase supply % is allowed as there is no deviation phase to phase or phase to ground.

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