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Forum Index : Electronics : watts vs rpm tests

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Haxby

Guru

Joined: 07/07/2008
Location: Australia
Posts: 418
Posted: 11:48am 07 Aug 2008
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Hi all,

I have some 80 series motors that I would like to use without re-wiring them. I'll be trying my PC power supply idea to see if it works as a variable 90v to 350V DC to regulated 12V DC converter. (well actually two of them for 24V)

Has anyone tested these 80 series motors with a variable load to see how much max power is produced at various RPM? If not I will do it.

My original idea was to link up around 10 of the motors all on the same shaft and connect them to a large blade to make one big 3KW generator but I think I will have problems namely:

The bigger the blade, the lower the RPM hence the amount of F&P motors will have to grow exponentially if I want a direct drive system.

Ideas or comments?

I did see a table somewhere outlining how much current each motor could handle but that was not what I am after. I am after the max power with respect to RPM of a standard unmodified 80 series motor.

If its low rpm power output is not good, I will have to think about gearing and that would be a pain.
 
CraziestOzzy

Senior Member

Joined: 11/07/2008
Location: Australia
Posts: 135
Posted: 10:47am 08 Aug 2008
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  Haxby said  
direct drive system.



Would be nice to know what you mean with that.
Aside from that, I have no experience with those motors (80 series) but would sure like to see your multi motor setup
http://cr4.globalspec.com/member?u=25757

http://www.instructables.com/member/OzzyRoo/
 
Haxby

Guru

Joined: 07/07/2008
Location: Australia
Posts: 418
Posted: 04:48am 09 Aug 2008
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Direct drive system = no gearing
 
GWatPE

Senior Member

Joined: 01/09/2006
Location: Australia
Posts: 2127
Posted: 12:17pm 09 Aug 2008
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Hi haxby,

The SMPS you are hoping to use will basically produce a constant output. These units are designed to produce constant outputs for a varying input. A windmill does not produce power this way.

I can see windmill loading problems.

The windmill output voltage and loading current should increase with increasing rpm, not be constant, or decreasing.

I have had most success with boost maximising. I hope to test a buck version soon. I envisage combining a boost cct with a commercial buck type cct will be a good combo as well.

The difficult mill maximising function has least problems when a variable gain boost topology is adopted.

Gordon.

become more energy aware
 
oztules

Guru

Joined: 26/07/2007
Location: Australia
Posts: 1686
Posted: 02:30pm 10 Aug 2008
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Haxby, if you are using unmodified computer supplies, then what Gordon says is true.

If you modify them as Dinges has done, then you may well achieve part of what you are after. Then you can set an unrealistically high voltage (say 16v per psu) at a high current limit, say 15A per unit) and the supplies will charge according to the amount of power available to the input.
This is achieved by both the tl494 pwm op amps (which you now have control of, and the changing voltage on the inputs which restricts the power transfer if the voltage drops below what can drive full power (about 150v or somewhere thereabouts from memory for 240v setting).

If you were to expect more power than this from the mill, then more supplies are in order.

How you match this to the blades is more complex... and frankly above my head at the moment. I will have to give this some more thought. I think we may be in danger of stalling it out too easily. You might have to control the deadtime pin with some feedback, but i don't know which way to jump at the moment.

Best of luck with this, we may all learn something.


.......oztules
Village idiot...or... just another hack out of his depth
 
Haxby

Guru

Joined: 07/07/2008
Location: Australia
Posts: 418
Posted: 12:48am 11 Aug 2008
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I mentioned my approach in a different post but I think its best done by measuring the wind speed with a separate instrument, and ensuring the RPM of the wind turbine is matched to its efficiency band. This can be done by PWMing the batteries from the output of the power supplies. A picaxe could easily do this via a lookup table.
 
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