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Help with lowering voltage

Discussion in 'General Electronics Discussion' started by Tezza1, Dec 9, 2011.

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  1. Tezza1

    Tezza1

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    0
    Dec 9, 2011
    Hi All: I need to get 350v DC! I have a 500vac transformer connected to a bridge rectifier which gives me 470v DC how can i bring it down even further to 350v DC? would i be able to do it with diodes if so what type of diode?. As you can see i am new to electronics so i'm asking for your kind input & help & not hurtful comments. Thanks. Tezza :) Any help would be welcome.
     
  2. davenn

    davenn Moderator

    13,439
    1,808
    Sep 5, 2009
    Hi tezza
    welcome to the forums :)

    no you cant do it with diodes

    for dealing with that sort of large voltage. the best choice is still to get the correct transformer.
    What is the 350V going to supply ? will you need smoothing capacitors after the bridge rectifier ?
    answers to that will determine the correct secondary voltage choice for the transformer

    Dave
     
  3. Tezza1

    Tezza1

    18
    0
    Dec 9, 2011
    I thought that would be the case but thanks for the conformation davenn, looks like more $$$ on a new transformer! Cheers
     
  4. duke37

    duke37

    5,283
    737
    Jan 9, 2011
    When an AC source is rectified and fed to a capacitor, you get Vac * 1.4, thus 350V will give 490V.DC.
    If a choke is interposed between the rectifier and the capacitor, the output voltage will be Vac * 0.9 thus 350V will give 315V.
    Finding the right choke may be difficul, it will need to be sized correctly for the application and should have a small resistive load to stop it behaving as a capacitor input filter.
    Choke input filtering is used in more powerful applications since the current is almost constant unlike the capacitor input filter where the current occurs in large pulses.
     
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