variable frequency power supply

Discussion in 'General Electronics Chat' started by relicmarks, Nov 17, 2008.

  1. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    Whats the theory behind a variable frequency DC and AC power supply

    1.) What controls the frequency to make it variable frequency in a AC to DC power supply?

    2.) What controls the frequency to make it variable frequency in a AC to DC power supply?


    Most in my electronic books the frequency in the power supply is FIXEd set to 50hz or 60hz , but how can i make it variable?

    transformer,rectified section,filter section, regulator section

    Half wave rectifiers are 50hz?
    Full wave rectifiers are 60hz?
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    Your question is not clearly understood at least by me. Write it better please.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    The power company controls whether their AC power output is 50Hz or 60Hz; in the USA it's 60Hz, Europe is primarily 50Hz.

    Linear power supply manufacturers design the transformers so that they can be used across a fairly narrow range of frequencies (say, 47-63Hz), but still be reasonably efficient.

    Switching power supplies are different animals, and generally run at much higher frequencies (perhaps 50kHz-3MHz). Some newer designs are using FM to reduce narrowband EMI.
     
  4. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    Some power supplys DC power supply or AC power supplys have a variable frequency parameter knob

    Most variable frequency DC or AC power supplys are to control AC or DC motors

    How can you take a regular DC power supply and AC powers supply and add this variable frequency knob?


    Power supply block diagram:
    transformer,rectified section,filter section, regulator section

    What sets the frequency? and how can i make it variable ?

    A Half wave rectifier is at what frequency? before the filter caps
    A Full wave rectifiers is at what frequency? before the filter caps

    60hz 120 volts AC input into a Half-wave rectifier , the frequency would be 30hz? because it rectfied the 60hz into 30hz

    A half wave rectifier LOWERS the input frequency right?
    A full wave rectifier Increases the input frequency by double

    60hz 120 volts AC input into a Half-wave rectifier , the frequency would be 120hz? because it rectified the 60hz into double a octave up
     
  5. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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  6. mik3

    Senior Member

    Feb 4, 2008
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  7. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    no they aren't switching power supplies

    They are variable frequency power supplies very different
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    Walters (I know you), please learn something (anything!) about electronics.
    This is your 3rd forum for your millions of questions?

    A variable frequency needs to have a variable frequency generator circuit that is called an oscillator. A current amplifier is added so it can drive an AC motor.
    You can look on Google for a description of a half-wave rectifier and a full-wave rectifier that is completely different from what you say.
     
  9. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    the fundamental frequency of the ripple voltage is twice that of the AC supply frequency (100Hz) where for the half-wave rectifier it is exactly equal to the supply frequency (50Hz).

    Thus when operated from a 60-hertz line, the frequency of the pulses is 60 hertz. This is called RIPPLE FREQUENCY.

    The ripple frequency at the output of the full-wave rectifier is therefore twice the line frequency.

    The higher frequency at the output of a full-wave rectifier offers a distinct advantage: Because of the higher ripple frequency, the output is closely approximate to pure dc. The higher frequency also makes filtering much easier than it is for the output of the half-wave rectifier.

    ::Ripple frequency chart::
    Ripple frequency for half-wave rectifier is 50hz to 60hz
    Ripple frequency for full-wave rectifier is 100hz to 120hz
     
  10. scubasteve_911

    Senior Member

    Dec 27, 2007
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    Going to have to agree with you on this one.. Honestly too many questions from one person to keep up with.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    Trying to answer his questions reminds me of Heracles and the Hydra. :rolleyes:

    Anyone have a torch? ;)
     
  12. scubasteve_911

    Senior Member

    Dec 27, 2007
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    lol, excellent analogy ! Maybe this is the torch of this thread? Or, perhaps he will continue undiminished.

    You would think someone that determined to learn would pretty much know anything, unless it is a recent fad?

    Steve
     
  13. Audioguru

    New Member

    Dec 20, 2007
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    Walters was banned from at least one website for making too many simple and stupid questions. He is (was) on a few forums with exactly the same du[plicated simple basic questions.

    He started by asking questions about the index of a book. The book had the simple answers that he didn't understand.
    Maybe he should do flower decorations instead of electronics.
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    I sure don't mind people asking questions; after all, that's what this site is about.

    But this particular poster seems to hammer away relentlessly, often in multiple threads. Then he'll reply to his own thread with some random items he found in searches, then ask more questions.

    It's as if the answers given aren't quite registering, and meanwhile the goals keep changing. :confused:

    I don't wish for him to be banned, but I certainly wish he would take more time to research subjects before simply posting a rapid-fire series of questions - and if he can't find an answer, then try to form the questions more completely.

    There are plenty of folks that would like help with various things, and it seems that the helpers a tad busy this time of year. Better that we try to help more folks, than concentrate on one person.
     
  15. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    sorry about all the questions

    but there is a such thing as power supplys with variable frequency as i gave the hyperlinks too

    i guess these special power supplys are some type of function generator

    or they are using a function generator as a power supply
     
  16. scubasteve_911

    Senior Member

    Dec 27, 2007
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    lol, sorry for the questions, here's one more!
     
  17. John Luciani

    Active Member

    Apr 3, 2007
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    The variable frequency power sources are AC power supplies. An AC power supply
    is essentially an amplifier + function generator.

    (* jcl *)
     
  18. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    yes i just read that if you hook up your AC function generator up to a power amp its what they call a variable frequency power supply

    The variable frequency power sources are AC power supplies. An AC power supply
    is essentially an amplifier + function generator.


    Is this what u ment by amplifier + function generator?
     
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