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  1. #1
    Join Date
    May 2004
    Location
    Malden Mass
    Posts
    288
    Hi Everyone,
    I had a question regarding a 250 volt transformer thats step down voltage to 24 volts. If I am reading 32 volts or more ,is the transformer bad?

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,058
    Sounds like you wire a multi tap transforemr for the wrong voltage.
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  3. #3

    What is your input voltage, 250 volts?

    Check/change the batteries in your multimeter.

  4. #4
    Join Date
    Jan 2003
    Location
    Kentucky
    Posts
    2,651

    Talking

    yep.....i have never seen a 250volt transformer...usually go with a 240volt....could not resist






  5. #5
    Join Date
    May 2004
    Location
    Malden Mass
    Posts
    288
    ok sorry 240 volts or 250 volts, I dont have the transformer in front of me, But I read the voltage correctly ,because I tested a nearby 120 volt transformer and it read close to 24 volts on the output side.

  6. #6
    Join Date
    May 2004
    Location
    Malden Mass
    Posts
    288
    In regards to imput voltage ,one leg reds 117 volts and the other leg reads 117 also, output reads 32 volts.

  7. #7
    Join Date
    Jun 2003
    Location
    southeast USA Occupation:HAVC tech
    Posts
    552
    most stepdowns I deal with are actually 27 volts secondary.. I've had em as high as 33 volts and have never had adverse effects... no biggy here in my opinion.
    AJS
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  8. #8
    Join Date
    May 2000
    Location
    Monmouth Junction-NJ-USA
    Posts
    6,004
    ditto to what AJ said. Lots i read are 30v
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  9. #9
    Join Date
    Oct 2005
    Location
    Fairfax, VA
    Posts
    111
    The xfmr may have primary taps for 208 and 240 v. If you have 240 feed, measured line to line, then it should be connected to the com and 240v tap. Some mfrs have a 27v max, others don't.

  10. #10
    Join Date
    Jun 2002
    Location
    Bemidji, Mn
    Posts
    3,573
    Never seen one over 27 myself. Might be tough on a coil, but I really dont know!
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  11. #11
    Join Date
    Apr 2004
    Posts
    7,680
    I cant see how you can get the wrong voltage out if the input voltage is correct and the transformer is correct.

    The secondary is a function of the number of turns inside the transformer compared to the primary. For instance a 240 to 24 transformer has 10 times as many turns in the primary side as does the secondary. (the primary wire is generally much thinner so this can be accomplished, and thats whey the primary burns out when your short the secondary).

    So if you take this same transformer and apply 250v, the secondary will only be 25v. Even a 208v-24 transformer would only give you a 28.8v secondary if you applied 250v.

    In order to get 30+ volts you either have the wrong transformer, there is a slight short within the primary windings that actually parallell a few turns, or your meter is in need of calibration. The only other cause would be that you are getting some sort of back EMF from a close by motor in the primary circuit.


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