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Thread: industry standards for minimum Megger test acceptability

  1. #11
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    1000 v to gnd ~ 0.24 mA at 4.1 Mohm
    I assume machine voltage is 480 so 277 to ground or 0.07'm
    ok imo

    a rebuild may not include a rewind
    only a cleaning and baking

  2. #12
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    Quote for rebuild stated: removal of old coils and potting compound, winding of new coils, new potting compound, new bolts, contact ring included. Chuck will be tested before shipping.
    So, am I to assume this rebuild does not meet the minimum industry standard?

  3. #13
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    what is the operating voltage of the machine?

  4. #14
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    act R = k x 11.1

    0.22 from chart or 1/2 for every 10 C drop
    65 F = 18.33
    40 - 18.33 = 21.67
    k = 10/21.67 x 1/2 = 0.22 or 0.5^(21.67/10) = 0.22

    act R = 0.22 x 11.1 = 2.47 Mohm
    std is 5 Mohm

    ref std IEEE Recommended Practice for Testing Insulation Resistance of Rotating Machinery, IEEE Standard 43-2000.
    Last edited by Ingenieur; 03-08-18 at 03:09 PM.

  5. #15
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    can you email me a copy or direct me to the "chart" where you got the .22 value you used in the formula to correct for temperature? Thank you.

  6. #16
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    Quote Originally Posted by rick56 View Post
    can you email me a copy or direct me to the "chart" where you got the .22 value you used in the formula to correct for temperature? Thank you.

    here's one used in a whitepaper http://www.netaworld.org/sites/defau...-%20Bishop.pdf
    the chart uses act temp in deg C

    the equations yield the same result
    act temp in deg C
    corrected temp = 40 - act temp

    k = (10/corrected temp) x 1/2
    k = 0.5^(corrected temp/10)
    Last edited by Ingenieur; 03-13-18 at 11:50 AM.

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