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Polyphase rectifier: Calculating the diodes needed.

  1. Sep 10, 2009 #1
    Hello,

    I have created a theoretical coil of
    170 turns*.4871 Tesla's*.0045m^2/.06 seconds=6.21V (Faraday of course.)

    ohm's of the coil=.405
    6.21V/.405ohms=15.33A

    The equation I used
    -N * curl*B*A/curl*t
    N=number of turns; B=Tesla's; A=area of the coil; t=Time; curls cancel out.
    (To calculate Time I used 1000 rpm/60=16.666 rps;1 second/16.666 rps=.06 seconds)
    (To calculate Tesla's I chose a magnets surface gauss, 4871 and converted to Tesla's; 10,000 gauss=1 Tesla)

    Lets say I have 9 coils with 3 phases:
    http://www.allaboutcircuits.com/vol_3/chpt_3/4.html#03267.png
    How do I calculate the Diodes I will need for the 3 Phase Rectifier? (see above link for schematic.)
    If I had more phases will that change what diodes are needed? (see above link for 6 phase schematic.)
    What voltage and amperage ratings for diodes?
    What reverse voltage ratings for diodes?
    Will the voltage drop across the diodes depend on the diodes I choose for the system?
    Is a dump load nescessary if I were charging batteries and the batteries were full?


    After rectification 111.78Vdc @ 46A. (This does not account for any voltage drop through the rectifier.)

    Google seems to return non pertinent info about calculating for diodes.
    Would Wolfram Alpha be better in this area?

    P.S.

    My goal is to understand the generating of Alternating Current and it's conversion to Direct Current.
     
    Last edited: Sep 10, 2009
  2. jcsd
  3. Sep 11, 2009 #2
    My voltage and amps out is incorrect.
    For the 3 phases it's 37.26 Volts and 46 Amps

    I checked mouser form the first sticky for diodes.
    I know that diodes allow voltage and amps to travel in one direction and prevent it going in the opposite direction.
    My Volts on one side is 18V the other side 37V. Reverse Voltage I think would be 37V.
    Second, Continuous current through the diode. I have 15 Amps.
    I think I need a diode that would handle <37V and at least 15A.
    I found Power Diodes from 200V reverse and 16A continuous up to 1400V reverse and 16A.
    Voltage drop for all of these is 1.2V per Diode.

    Would the 200V, 16A be sufficient?

    If I add 3 more phases for 6 phases total that would be 37V @ 92A. Is this correct?

    I also noticed the higher the Tesla's the more current produced.
     
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