pmdc motor for generator

[58gm58]

hello, I am new to this so please don't laugh to loud. I would like to build a turbine with a motor that I have. It is a DC Servo Motor that is tagged: 2000rpm,108V,12 amp,5.4 Nm. It is a brushed motor.My questions are, what size blades would I need, what type size/ controller,how large a battery bank voltage ect? Or am I just crazy? Thanks

[SparWeb]

No laughs, just welcome aboard.

Scale down the voltage to the battery voltage you choose.  Let's say 12V for the sake of the example, and it's the most common anyway.

If 108V turns the motor at 2000 RPM, then logically turning the motor at 2000 RPM, you might expect to see about that much voltage (not exactly, usually a bit less).

To turn it fast enough to get 12 volts, then:

12/108*2000 = 222 RPM.  Probabaly a bit faster in reality.

That speed, 222 RPM, is the cut-in speed of the motor - now acting as a generator.  It will be producing enough voltage to start to charge the battery.  It sounds reasonable enough so you probably have something worth trying.  A great start to experimenting and trying out your ideas.

Good luck!

Here's a link to the FAQ on the topic, too.

http://fieldlines.com/board/index.php/topic,143574.0.html

[Perry1]

Welcome aboard. Might I add that you will want about 13- to 13.5 volts to charge that battery given the diode losses you will see. A diode must be used in order to keep your new servo 'generator' from acting like a motor again.
Another useful piece of information is the current rating of the motor which is 12 amps. Given this, you can predict that your gen will put out 13.5V x 12A = 160 watts of power. Now you need to match a blade set to give you that.

Perry

[taylorp035]

I am guessing something closer to 5-6ft may do the trick.  It may take a a second set to get the best results after watching it spin for a few weeks.

18.5 rpm per volt is pretty good IMO, so you should be happy with that motor.