home

news
new innovations

articles
diy instructions
your projects
ideas
urban influence
use green

forum
greenstore
links
contribute


 

ReWiring a Fisher and Paykel Generators/Alternators.


So now we have our output coming out successfully from our rewire generators but it's 3-phase AC power, which most of the time, at 12 volts, you want as DC. So how do we convert it from AC to DC? With Bridge rectifiers. So grab yourself two bridge rectifiers that can support at least 15 amps. This is a 35 Amp one that we picked up for about $5 each.
35 Amp Bridge Rectifier 35 Amp Bridge Rectifier Bridge Rectifier Diagram

First we'll learn how to wire it so that those that don't care how it works can drop out. Then we'll explain how it works.

Attach the three AC outputs to the rectifiers. Then we want to wire the positives together and to an DC positive output wire and attach to the rectifiers. Then wire the negatives together and to a DC negative output wire and attach to the rectifiers. Like so...
3 Phase AC to DC Circuit Diagram

It's that easy but make sure your bridge rectifiers are mounted to a heat sinc and greased with a heat sinc compound to protect them.


But how and why does it work. Bridge rectifiers are basically a bunch of diodes strung together. Diodes only allow current to pass in one direction. So where AC power has current passing in one direction and then the other like so...
AC Power Graph

We now want it to only go in one direction. If we added a diode to one wire we would only get the forward (positive) power coming through. Which would look something like this and would look like us turning DC power on and off continuously...
AC Power through Diode Graph

Now 3 phase AC power, such as we having coming out, are produce power these AC currents like above but they are perfectly out of time with each other, as one is going negative the other is going positive like so...
3 Phase AC power graph

Now if we attach diodes to each of them allowing power foward and join the ends of the diodes together, we get an output of the peaks of all the AC power waves (the red line below). And if we attach diodes again to each but this time in the reverse direction we get an output of all the troughs of the AC power waves (the black line below). So at the end if we have a look at the red and black lines we can see two DC outputs positive and negetive....
3 Phase AC dioded power graph

Bridge rectifiers are diodes already wired together for us as you can see below. And, Yes you can by 3 phase ones but for some reason the are really expensive, so these are a much better option.
Circuit Diagrams



 

[ give feedback ]              [ subscribe to news ]              [ email yourgreendream ]