A question about generating electricity from a turbine

[90mos90]

I'm building a turbine, and I'm using a hoverboard wheel as a generator.
I want to check the electrical output from the turbine, so I connected the turbine to another motor that will turn it, and it will be measured with a voltmeter, about 30 volts.

To measure amperes as well, I can measure amperes in series connection.

Then I saw that when I connect the lamp, immediately the turbine slows down, and spins more slowly, and the measurement also dropped to about 20.


Can someone explain to me why when I connected a lamp it slows down the rotation of the turbine?

[Bruce S]

Welcome aboard;
What you experienced is perfectly normal.
The first reading was what's refereed to as open voltage. The second is reading under a load.

There are few other math calcs you will need to have to know what kind of output you will be able to see from this motor.
I believe there is another posts on here about using the same style motor.
Do a quick search , it's a fairly recent post too.

Question MOS90? ARMY?

Cheers
Bruce S 

[90mos90]

Ok.
So when I want to find out how much electricity the turbine produces, what is the real test, open voltage or under a load?

[90mos90]

Ok.
So when I want to find out how much electricity the turbine produces, what is the real test, open voltage or under a load?

[Bruce S]

Under a load is best. Open voltage is usually only to know that the unit is working.
However, there is a few other measurements you will want to have handy.
What is the RPM of the motor you are testing when you get the volts?
This will help a ton when you start needing to know at what speed it will need to be at to start producing the output you are looking for.

Hope this helps
Bruce S

[Adriaan Kragten]

If no electrical load is connected to the generator, it needs almost no torque to rotate. This means that the windmill rotor is running unloaded and so it runs at the unloaded tip speed ratio lambda unloaded. This results in a certain unloaded rotational speed for a certain wind speed. The windmill rotor produces maximum power if it runs at the design tip speed ratio lambda design. The design tip speed ratio is about a factor 5/8 of the unloaded tip speed ratio (see my public report KD 35 formula 6.4). So this means that the generator must be loaded that much that the unloaded rotational speed at a certain wind speed is reduced by a factor 5/8 at that wind speed to get maximum power out of the rotor. If the generator is loaded too strongly, so if the rotational speed is reduced more than a factor 5/8, the power coefficient Cp of the rotor will become less than maximal because then you come at the left side of the Cp-lambda curve (see report KD 35 figure 6.7).

The produced electrical power is the product of the voltage times the current so Pel = U * I. At open voltage, the voltage is maximal but there is no current so the power is zero. At short-circuit the current is maximal but there is no voltage and so the power is zero too. There is a certain reduction of the open voltage for which the electrical power is maximal. This voltage is about 2/3 of the open voltage (see measurement executed on a PM-generator given in my public report KD 78). It is not necessarily so that the maximum electrical power coincides with the maximum Cp of the rotor. Matching is explained in chapter 8 of my public report KD 35.

[brandnewb]

Dear Adriaan,

There is no denying that you know more about the field than any of us ever will.

But may I politely ask you to sometimes take into consideration newcomers like us?

I will speak for my self now. I get intimidated very quickly when I read your in depth responses.

Sometimes all we want is a quick and dirty solution to what seems a not so complex problem.

I'll understand and accept that I might be mistaken here in where there simply is no other way than complex to go about things. If so then please accept my humble apologies.

[Adriaan Kragten]

Dear Adriaan,



I'll understand and accept that I might be mistaken here in where there simply is no other way than complex to go about things. If so then please accept my humble apologies.

This is just the problem with questions asked on this forum concerning matching in between rotor and generator. There is no simple way to explain matching but I have tried to do it in chapter 8 of my public report KD 35. You need to know the characteristics of the rotor and the generator. To describe the characteristics of the rotor, at least you have to understand that any windmill rotor has an optimum cubic line. The formula for the optimum cubic line is given as formula 8.1 of KD 35. The Cp of the rotor is maximal if the optimum cubic line is followed. The characteristics of the generator are only known if you have performed rather complicated measurements (which include measuring of the torque) which finally result in a certain Pmech-n curve for a certain load. Optimal matching is gained if the Pmech-n curve of the generator for the wanted load is laying as close as possible to the optimum cubic line of the rotor. 

[brandnewb]

I will accept then that wind power generation is only for the intellectual people and for the fools like I am.

The common man beter stay clear of this field.

I will share my results gathered by the fools approach.

[Bruce S]

I will accept then that wind power generation is only for the intellectual people and for the fools like I am.

The common man beter stay clear of this field.

I will share my results gathered by the fools approach.

This as Absolutely incorrect!!
Throughout the years I have been on this forum, no less than a dozen people have come here and took the information posted from fellow member and learned and had either successfully built and posted their results. Still do in fact.

SO saying the "common man" better stay clear of this field borders on taking the easy way out.
AND will quickly get on the bad side of people honestly trying to help you out 

Build a turbine however you wish, just DO NOT down play the efforts others have done or the help being freely given.

I would suggest going there and taking the time to read the information
Adriaan has gone to great lengths to put as much FREE information on his site.

Also, there are in fact a few u-ber's who come here to get the answers to their questions only to post them on their sites with no acknowledgement to this forum.
 

Bruce S

[Mary B]

I will accept then that wind power generation is only for the intellectual people and for the fools like I am.

The common man beter stay clear of this field.

I will share my results gathered by the fools approach.

There are several tried and working designs here you could pick from. Heck get your hands on a surplus washing machine pancake motor and the magnet drive rotor that tit uses. Rewire to fit your battery voltage, add a set of blades and put it up. It WILL generate power.

5m/s winds will not have a lot of power in them to start with so don't expect kilowatts from a machine that you can afford to build! 200-300 watts is maybe doable leaving the motor stock and using MPPT to match the high voltage off it to your batteries.

F&P pancake motor http://www.randysworkshop.net/order.html plus her has a design for a mount for it, just ask him! Look around his page for ideas!

[JW]

I will accept then that wind power generation is only for the intellectual people and for the fools like I am.

Its not a fixed discipline, It it varies from steam engines to gasoline generators and hydro machines then solar and inverters and batt banks etc.

The most important thing is matching load, and optimize the best alt impedance. Heat is lost and the gen assy dissipates heat in its windinge but is not a big deal. The thing too understand is usually the gens are within a parameter at regular operating temp like 100 f or more its not too critical on these generator's/alts generally the flux pathways and magnetic field strength and thick conductors low impedance seems to be more important. Eddy currents are important to.

Ohms law is your friend...
   

[JW]

for real, your database is massive. For newcomers like my self it is easy to get lost in it. No disrespect meant but the sheer size of it can be intimidating.

I have practically memorized it.

https://www.fieldlines.com/index.php?topic=128373.0
https://www.fieldlines.com/index.php?topic=138138.0
https://www.fieldlines.com/index.php?topic=137088.0
https://www.fieldlines.com/index.php?topic=127288.60;wap2

That last one is related to a good topic but is the beginning of data loss.


Here is me

https://www.fieldlines.com/index.php?topic=143318.0

An important thing is that I own the site here. Bought it from DanF and DanB. Thats why I put so much into this site.

[brandnewb]

I will accept then that wind power generation is only for the intellectual people and for the fools like I am.

The common man beter stay clear of this field.

I will share my results gathered by the fools approach.

This as Absolutely incorrect!!
Throughout the years I have been on this forum, no less than a dozen people have come here and took the information posted from fellow member and learned and had either successfully built and posted their results. Still do in fact.

SO saying the "common man" better stay clear of this field borders on taking the easy way out.
AND will quickly get on the bad side of people honestly trying to help you out 

Build a turbine however you wish, just DO NOT down play the efforts others have done or the help being freely given.

I would suggest going there and taking the time to read the information
Adriaan has gone to great lengths to put as much FREE information on his site.

Also, there are in fact a few u-ber's who come here to get the answers to their questions only to post them on their sites with no acknowledgement to this forum.
 

Bruce S

I did not mean to offend Bruce, My appologies.

Sometimes I do not know how to express myself.

I feel sometimes that what should be simple and quick and dirty ends up rather complex and therfor not feasable for 'normal' people.
I meant either one is smart and able to understand the finer points and thus stand a chance.
Or just lime me just plow through not knowing anything and seeing where the ship strands.
No ill intend here at any time. I never had any ill intend by the way here ever.

So if I unintentionally ruffle feathers the wrong way that is kind of what it is I mean. In where it can feel sometimes like a special club that I am not a part of yet and have to speak a certain lingo in order to be accepted into it.

I am just a simple guy with simple building means looking to generate some power. If one can help then I am way thankful and if one is interested in my results then of course I will be super proud to share any I have. haha well that is if they are any good of course
If the results suck then I will still share, albeit with a bit of a blush on my cheeks.

Anyway, let's make love, not war and i will be sure to keep plowing through and ask more questions.
Thanks guys!