selection of transformer

Discussion in 'The Projects Forum' started by vead, Dec 15, 2011.

  1. vead

    Thread Starter Active Member

    Nov 24, 2011
    621
    8
    hiiiiiiiiiiii

    i need transformer for 12v dc 2a
    can i use this formula for transformer secondary voltage

    Vsec(rms) = (Regulated DC + Regulator Drop + Ripple voltage + Rectifier Drop)/√2

    where, regulated dc=12vdc
    regulator drop= 3v
    ripple voltage=1v
    rectifier drop=1.4v

    Vsec(rms)=12.30ac

    if any mistakes please correct me
     
  2. k7elp60

    Senior Member

    Nov 4, 2008
    478
    69
    You are pretty close. I would use a standard transformer that has a secondary voltage of 12.6 volts. But the transformer must have a secondary current rating of 3.3 amps or you will have excess heating caused by brute force filtering. With brute force filtering(bridge rectifier to filter capacitor then regulator) the charging current will be load current/0.6= 2/.6 or 3.33A. I think the closest off the shelf transformer would be 4A secondary.
     
    vead likes this.
  3. vead

    Thread Starter Active Member

    Nov 24, 2011
    621
    8
    hii

    i cann't understand
    how can i calculate current rating of transformer
     
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