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Thread: Box fill question and DC motor question.

  1. #1
    Join Date
    May 2012
    Location
    Miami
    Posts
    54

    Box fill question and DC motor question.

    Hi there!, please I need to solve this two questions, I having trouble with them, looks very simple but there is something I cannot find right. Thank you !!!!!




    1. What size of box is required for two #6 conductors, one #10 ground that leave the box, one #12 ground and two #12 conductors, the #6 conductors has internal clamps and the #12 has external clamps.
    2. what is the efficiency of one 5HP/230 DC motor ?

  2. #2
    Join Date
    Jul 2012
    Location
    Simpsonville, South Carolina
    Posts
    1

    Box Fill Calculation

    I gave your question about box fill a shot; Let me know what you think.

    TABLE 314.16(B) ALL OF ARTICLE 314.16

    2- #6 conductors = 10 cu in
    1- #10 ground = 2.5 cu in
    2- #12 conductors = 4.5 cu in
    1 internal clamp (#6) = 5.0 cu in
    Total: 22 cubic in = 4 x 2 1/8 square box



    for your motor question, I don't think there is enough info. Efficiency = output of true power/ input of true power

    the true output of a DC 5HP, 230v motor is: 1hp = 746watts; 5 * 746 = 3,730watts

    Let me know if this helps.

  3. #3
    Join Date
    Jul 2012
    Location
    Arizona
    Posts
    1

    Dc motor effciencies

    I have an old American Electician Hand book and it gives some approximate Eff: 5HP at half load 77% Full load 81.5 % hope this helps some

  4. #4
    Join Date
    Sep 2008
    Location
    UK
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    6,439
    Quote Originally Posted by AZBob View Post
    I have an old American Electician Hand book and it gives some approximate Eff: 5HP at half load 77% Full load 81.5 % hope this helps some
    I'm pretty ancient and I've dealt with quite a lot of DC drives. Not very often as small as 5HP but those figures seem like a reasonable basis for calculations.

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