Ametef 30V efficiency

[Perry1]

Hello all,

I have finally been aboe to do a little work on my 30V based turbine. Config is Ametek 30V PMG and 25" TLG blades, Dataq daq system. Right now just feeding into 1 125 Ahr DC battery.

So I am trying to make some spreadsheets of performance, I just (way later than I should have) noticed that I need to spin it up with a drill/lathe to a pretty high rpm to get it to 12 V. Here's my noobie revaluation. I hooked it directly to my 12V battery and while still at 12V it spun way slower. Way slower. OK, now that this has happened it seems completely intuitive. I think what I am seeing is the generator efficiency in the classical wind turbine power formula.

My question, what is the best way to characterize my PMG's efficiency? I can measure rpm with a tach for a given voltage or measure driven voltage at a given rpm?

Any help?

Perry

P.S. yes, I did use the google search first

[Perry1]

I know you guys need some data to properly comment. Here is a plot of the voltage vs. rpm curves for the turbine driven at a given voltage and the voltage against driven rpm. Hope this helps illustrate my point.

So how do I calculate efficiency of the PMG?

Perry

[Perry1]

I'm sorry, I can't get a simple picture to post on this thread. Am I an idiot? Could be but it's the only board I know where this is so hard. Sorry.

[Perry1]

Admin, I know this prob isn't your job but if you feel inclined could you attach my 30V.jpg file to this thread.

Thanks,

Perry

[ghurd]

Will a link to the chart do?

http://www.fieldlines.com/images/scimages/13340/30V.jpg

Not sure what you mean by efficiency.

Need to test input power vs output power.  Prony brakes, etc.

I always found they need to spin faster to make 12V, than the RPM they turn themselves while running on 12V.

Some people say they may make more voltage turning one way than the other.  My drill press only spins one direction.

Your findings seem kind of drastic for a 30 though.  I didn't think they were that far apart.

This 30 wouldn't happen to be from ebay's 'fuzzy logic', the sticker has square corners, and the shaft end is drilled and tapped?

Or possibly came from an ebay guy in SC with military logos all over his listings, who is no longer a registered user?

On a good note, the 13V mark is about right for a decent Ametek, 13V at about 375RMP.  A little high, but could be worse.

Something else can make them turn slower with 12V too.  Gunky grease in the bearings, possibly something related to the brushes, etc.  Remember, that is an old motor.

I found running them with 12V for a few hours, or a couple days, picks up the speed.

It also lowers the current required from the battery.

I measure the amps from the battery, then again in a few hours.  If the amps drop, then the motor is sort of freeing up.  I keep it going until the amps don't change.

I expect that will get your chart to match up a little better.  But in a bad way because the Blue line will move closer to the Purple line.

G-

[TomW]

[Perry1]

Thanks guys for the info and for helping out with my posting woes.

What got me going on this is watching all those ebay guys that sell motors rated at (for example)200V and 10 amps insinuating they are 2kW generators. I'm kinda a closet crusader against all the ebay/youtube misinformation. So I started doing a little research on my 30V to define the relationship power to spin a motor up to a cut in speed vs. power produced at that same cut in speed. I'd like to figure out a way to do this measuring only voltage and RPM. Have to think about it and see what variables drop out. I understand that a dyno or prony brake is the way to determine the motors efficiency but it was late, I had a few beers, and the prony brake store was closed for the night.

I checked my 30V to make sure it wasn't an ebay re-label. Thanks to this board and the heads up. Mine has no sticker, the information is printed directly on the motor. No tapped shaft either.

I'll run the motor for a day or so and measure the amps. Interesting experiment. We'll see if this motor loosens up a bit.

Perry