Using a brushless D.C. motor as a generator.

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Well-Known Member
Nov 7, 2012
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Victoria Australia
If you want to make a generator for your model engine to run then brushless D.C. motors are very common these days. Most photocopiers and laser printers have them. Older server computers have them in their back up drives. The one I used came from a laser printer. This generator has a three phase output so it has three wires to connect to your load. the maximum output voltage is 15 -18 volts. You could use only two wires for a load but you are wasting 1/3 of the output.

To use three wires use Christmas decoration lights as they are a small load to try first of. Each light has two wires coming out of the socket so connect one of the three output wires to one of the two wires and the do the same to the other two lights. So you should have one wire left over on each light, just connect those three wires together and you are ready to go. If your model engine is powerful enough six or nine lights could be used.

There is another way to use the three phase output, rectify it to D.C. and you only need to have two wires to connect to your load. To do this you need two bridge rectifiers. Just connect two wires from the output of the generator to the A.C. connection points on the bridge rectifier. Then connect the positive terminal of the bridge rectifier to the other bridge rectifier positive terminal and do the same to the negative terminals. the remaining output wire is connected to one of the two A.C. connections on the other bridge rectifier. Then connect one wire of the positive terminal to your load and do the same to your negative terminal and it does not matter which bridge rectifier you use.

When I started using motors as generators I had no idea how to connect them up so there were plenty of videos on youtube to show you how it is done. What makes this generator unique is the stator windings can be moved in and out of the magnetic field so the output can be changed to suit your load. Three halogen down light transformers were used to transform 12 volts to 240 volts to show how power stations generate electricity for homes and industries. I find model generators very interesting to build and testing their performance. I lost interest in building model engines mainly because you need very powerful model engines to run these generators. Have a look at my video.


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