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  1. Miller1085's Avatar
    Miller1085 is offline Junior Member Pro Subscriber
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    NEMA 3R

    Quote Originally Posted by SecondGen View Post
    This could be b, c, or d but NEMA 4 would offer the most protection.

    https://testguy.net/content/158-NEMA...ical-Equipment

    NEMA 3R enclosures are compatible for both indoor or outdoor applications and holds the least demanding rating for outdoor use.

    NEMA 3R Characteristics:

    Protection against incidental contact with enclosed equipment
    Protection from falling dirt, rain, sleet and/or snow
    Drainage provision
    Protection against rain at a level higher than the lowest live part
    Alternate locking and latching mechanisms available

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    Quote Originally Posted by A_Powers1992 View Post
    To Whom it May Help:



    4.) Which XFMR test has the ability to magnetize the windings?

    a.) Power Factor
    b.) TTR
    c.) Excitiation
    d.) Zero sequence impedance


    Doble criteria my company uses states that a TTR test can magnetize the core, not windings. Excitation testing is to be performed before TTR for this reason.

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    Thanks

    Thank you for the questions. Some of these I did not know either. More stuff to study I guess.

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    Quote Originally Posted by rofo42 View Post
    Doble criteria my company uses states that a TTR test can magnetize the core, not windings. Excitation testing is to be performed before TTR for this reason.
    Excerpt from FACILITIES INSTRUCTIONS, STANDARDS, AND TECHNIQUES, VOLUME 3-31, TRANSFORMER DIAGNOSTICS

    CAUTION:
    Perform the excitation test before any direct current (dc)
    tests. Excitation Current Tests should never be
    conducted after a dc test has been performed on the
    transformer. Results will be incorrect because of
    residual magnetism of the core left from the dc tests.
    DC WINDING RESISTANCE MEASUREMENT is the largest DC test performed on the transformer. TTR and IR testing does not have the same power applied to cause significant magnetism.
    My practice has always been to perform Power Factor Testing before any other test. I've had arguments with techs that NETA says to perform IR test first or perform IR first to check condition of Xfmr to prevent unnecessary tests (neither I agree are important as the above caution). I've always performed winding resistance last, since that same test set has the ability to de-mag the XFMR.

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