Rectifiers in Parallel?

[seanchan00]

Hi Friends,

I am finishing a wind generator exactly like Tim's 10' diameter wind turbine

except my blades are 8 feet in diameter. I can source only 30 amp

rectifiers here and I have bought 4 pcs. Do I need to rectify mine in

parallels of 2 - 30 amp rectifiers to each phase for my wind gen?

Will 3 - 30 amp rectifiers, one for each phase suffice? I have wired

it STAR. I may add a DELTA/STAR switch later if power requirement

increases. Still has a suspicion my 8 feet blades are too small for my setup. It may stall.

SeanChan.

[libra]

Almost any alternator shop will have 100am rectifier modules with small heat sinks for about $20. I mounted one of these on a larger heatsink.

Hope this helps

Libra

[richhagen]

I am not sure of your exact setup, and I do not qualify as an expert on this, however, there have been several failures reported due to problems with the rectifiers overheating during prolonged periods of high wind.  I would overbuild the rectifier, and use the largest heat sink I could get my hands on.  I took what I thought was a large heatsink (10inches by 5.5 inches with about 1.25"fins) out West with me earlier this year and was surprised to learn from the Dan's that it would be marginal at best for a large 12V machine, although suitable for a 48V machine of the same size where the current would be reduced to 1/4th for the same power.  Derate the total amps that each rectifier can handle when parallelling them, I'm not sure what a proper percent would be, but 30% would seem relatively safe to me.  While the voltage drop across each diode goes up with increased current, which tends to even out the current across the parallelled rectifiers, this may not be an exactly even split across the diodes due to slight manufactuing differences between otherwise identical units.  For that reason you should derate them when connected in parallel.  Rich Hagen

[finnsawyer]

You need six rectifiers to properly rectify a star configuration.  The end of each winding has two rectifiers in parallel back to back connected to the winding.  The current flows up through one of the rectifiers, through two windings, and out through one of the rectifiers connected to the top winding.  The other two rectifiers will be back biased and not conducting at that time (for about a third of a cycle).  The roles of the rectifiers change over a full cycle as different combinations of windings conduct current.

[finnsawyer]

Replace rectifier by diode in the above comment.  A rectifier could have more than one diode.  You need six diodes to rectify the three phase star configuration.

[hvirtane]

You need six diodes to rectify the three phase star configuration.

Please see the picture below how

to make the rectifier.

- Hannu

[finnsawyer]

Just to clarify since some lines appear to be missing.  The left sides of the diodes as shown are connected to the negative terminal of the battery.  The right sides are all connected to the positive terminal.

[seanchan00]

Thanks hvirtane and Finsawyer for your inputs,

I am just reading this belatedly as I have new ideas that needed to be debugged. I have already made my rectifier with 6 units of 35 amp brige rectifiers and it is wired as in your diagram with bridge rectifiers replacing the diodes.

Question.

1. Can I now divide the output from the rectifiers equally by taking the Positve and Negative wires from three rectifiers on the left and three from the right to two different 12 volt batteries for charging?
   
2. Will the two batteries be effectively be separated from communicating with each other draing the good by the bad when not charging?
   
3. Will one shunt regulator work on one battery be enough or I need two shunt regulators? One on each battery?
   
   

SeanChan (:>)