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no image Sunday, November 26, 2017 by Deepak P

LC filter for a single phase full wave bridge rectifier

We designed a single phase AC(50Hz) to DC converter with a full wave half controlled SCR-Diode bridge rectifier and LC filter on DC side. The LC filter is mainly to limit output ripple. In addition to attenuate ripple which we calculate at full load; we intend to maintain good voltage regulation from no load to full load.

So we wanted to explore swinging choke option where inductance changes with load current (low current-high inductance; high current-low inductance) so that our system acts as a choke fed filter at no/light load condition & capacitor fed filter at full load thereby maintaining output nearly constant from no load to full load.

But we got to know from the manufacturer that a swinging choke only has a range of inductance change for a given change of current. Our current range from no load to full load is too much of a change and the real inductance will never coincide. Instead, we can add a resistor in series with the choke but will make up the loss.

Please suggest any other method to have good ripple attenuation along with good voltage regulation with a LC filter? 



I have seen people also doing as below.

LC Filter circuit as a option

Comments

  • by  Rick Curl
    Hi Deepak-

    There's a good paper about designing with swinging chokes here: Step-gap "E" core swinging chokes

    How much ripple is acceptable at full load?

    It sounds like you've already spent a lot of time and effort on the 50Hz design, but if this had been a switching supply, the power transformer and filter circuits would have been MUCH smaller!

    -Rick 

    • by  Deepak P

      Hi Mr. Rick

      Thanks for your reply..


      I have already seen the paper you referred; but I don't have the expertise to make it ourselves. 


      2% ripple is acceptable at full load.


      The only reason for using SCR power converter is that our customer needs only  this.


      - Deepak

  • by  Deepak P

    Hi Mr. Rick

    Thanks for your reply..


    I have already seen the paper you referred; but I don't have the expertise to make it ourselves. 


    2% ripple is acceptable at full load.


    The only reason for using SCR power converter is that our customer needs only  this.


    - Deepak

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