Fixed output transformers

Discussion in 'General Electronics Chat' started by ElectricMagician, Aug 2, 2013.

  1. ElectricMagician

    Thread Starter Member

    Jul 26, 2012
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  2. WBahn

    Moderator

    Mar 31, 2012
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    What makes you think that the output voltage is unaffected by the input voltage?

    If the input voltage drops 10%, then the output voltage will drop about 10%.

    If you think that it somehow magically allows you to hook up 120VAC, 208VAC, or 240VAC, then you didn't look very closely.

    See those four wires coming off the primary side? The black one is the common -- you always use that one. The wire that you connect to the other line is determined by the voltage. If you have a 120VAC input, you use the white wire. If you have a 208VAC system, you use the red wire. If you have a 240VAC system you use the orange wire. The blue and yellow are always the output, which is 24VAC provided you use the right connection and provided the actual input voltage is actually correct.

    Doubt me? Just look at the picture on the Grainger page.

    [​IMG]
     
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  3. ElectricMagician

    Thread Starter Member

    Jul 26, 2012
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    Oh okay, got it now. Thanks a lot
     
  4. WBahn

    Moderator

    Mar 31, 2012
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    Sure thing. Glad I could help.
     
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
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    You should also note that the specifications (numbers given on the rating plate or sticker) are for the transformer delivering a specified load current. This is usually the max continuous current available.

    Transformers' output voltage falls with increasing current delivery.
    So the no-load output voltages will be higher than shown, for a given input voltage.
    The actual variation of output voltage from no-load to full load is called the regulation of the transformer and usually given as a %.
    The smaller the % the better the quality of the transformer 10% is not unusual in the type of transformer you have shown.
     
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  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    At 40VA you will be limited to around 1.6a at 24v.
    40/24 = 1.66.
    Max.
     
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