Magnets and RPM

The spinning discs that hold the magnets, and magnet issues

Postby Mark on Tue Jul 24, 2007 3:24 pm

Dear friend,

we visited your web-site and we are very delighted.

There are so much interesting information and your
total presentation is great.

We are interested to make such generator and we are
looking for magnets and needed rpm.

Can you tell us how much rpm are needed for your wind
generator design?

Can you tell us exactly where you order the magnets
you used? Some link? and what are the dimensions of
magnet?

Your information from web-site are very useful.

Thank you for sharing your research with all of us.
Mark
 
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Postby windgat on Wed Jul 25, 2007 11:28 am

Hi Mark.

The magnets I use are 20x50x8mm. I got them from http://www.magnetech.co.za/ I would have liked to use bigger, but those were the biggest they had. Also, wedge shaped would be more effective, if you can find them!

The RPM needed depends on the voltage you want, and the number of windings in the coils. The more voltage, the faster RPM, and the more the windings, the less the RPM.

Using 9 coils of about 60 windings each, I can hand crank the generator (without blades attached) to get 60V (no load).

The longer the blades, the less RPM the wind will give you... this also depends on TSR (tip speed ratio).

A great thing is that the voltage acts as a natural brake, in other words the RPM will rise quickly, until the voltage of the system is reached, and then the power drawn acts as a brake, controlling the speed.

Hope that helps, and good luck!
windgat
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Re:

Postby jessica22 on Mon Sep 24, 2007 8:54 am

We are pleased to supply the magnet you needs. For wind energy, it is a hot topic and also a good solution to scarce resource. We are interested in it and have cooperated with some Germany company to provide the magnets and magnetic assembling they needed.

we have the CE certifcation and ISO 9001:2000. More than ten years in producing the magnetic products always be your trust supplier! we have attended the Coil, Transfer & Electric Motor Manufactory Conference in Germany. we are a company invested by Italy. Zhuji Ichoice Magtech Co.,Ltd is a hi-tech export-oriented enterprise, specializing in studying, manufacturing and selling of sintered NdFeB magnets and varieties of magtech products.For more information, please visit our website: http://www.hichoice.net/, http://www.bchoice.com.cn/.

Sintered NdFeB permanent magnets possess high maximum magnetic energy and high intrinsic coercive force. Zhuji Ichoice Magtech Co.,Ltd has the capacity of 800 tons per year.

Jessica.Long
E-mail: Jessica.long@hichoice.net or ldm112700@163.com
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Re: Magnets and RPM

Postby electron on Wed Oct 17, 2007 12:21 pm

Nice to see South Africans taking advantage of wind power, a wind farm should be set up in PE to take advantage of the natural atmospheric rotational winds that batter that coastline.
Problems to overcome are still acoustic noise losses and bird strike problems, and of course ignorance by locals.
Wind power like all other forms of energy, comes at a cost nothing is free so long term effects have to be monitored to see whether energy conversion or the natural air streams poses a problem on the environment over time?
There are no problems only solutions!!
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Re: Magnets and RPM

Postby windgat on Mon Oct 22, 2007 10:31 pm

Hi electron. Acoustic noise is a bit overrated as a problem I think. My generator is practically silent (the trees make more noise than the generator)

Bird strike is definitely overrated! I forget the figures, but it is something like domestic cats kill hundreds of times more birds a year than wind generators, yet no-one suggests we stop having cats...

Disrupting airflows is maybe an issue once a the amount of wind harnessed is more than negligible. A long way away I think. Also, a city disrupts natural air streams, so wind farms are not something new in that regard.
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Re: Size of blades

Postby Boerseun459 on Thu Jun 17, 2010 11:46 pm

[quote="windgat
The longer the blades, the less RPM the wind will give you... this also depends on TSR (tip speed ratio).

I was under the impression that one would get more RPM than with shorter blades :?: :?

With a 30km/h wind, for example, which turbine would preform best - the one with a 1.5m or the other with a 3m blade diameter (all other things being equal)?
Can you also explain what TSR is?


[quote="jessica22"]We are pleased to supply the magnet you needs. For wind energy, it is a hot topic and also a good solution to scarce resource. We are interested in it and have cooperated with some Germany company to provide the magnets and magnetic assembling they needed.

Windgat, is this chick talking about rare earth, or some other type of magnet? And did you ever took her up on her offer?

I`m probably going so sound incredibly stupid by asking this :oops: , but here goes...
The magnets found behind car speakers, ect, is this what you guys call "rare earth" ?
Where does these magnets come from?

I`m not messing with you, it`s just that I am a complete novice when it comes to windpower and I`m learning from scratch.

Thanx
Boerseun459
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Re: Magnets and RPM

Postby Boerseun459 on Sun Jun 20, 2010 6:35 pm

OK, so I`ve read up on magnets on the internet since my last post and now know a bit more. :lmao:
Found a lot of manufacturers who are willing to supply quotes on wedge-shape magnets.
How far apart should one place these magnets from each other on the same rotor?
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Re: Magnets and RPM

Postby windgat on Sun Jun 20, 2010 11:41 pm

They can be close together - the steel plate attracts them and keeps them very firmly in place. Its the relative layout to the coils that is important - see you post under Coil shape.
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Re: Magnets and RPM

Postby Boerseun459 on Mon Jun 21, 2010 9:41 pm

Thanx Windgat

So if I have my wedge magnets designed in such a way that there is only 5mm space between them, after placement on the rotor, will that be OK or is that too close?
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Re: Magnets and RPM

Postby windgat on Sat Jun 26, 2010 11:56 am

I would say that's ok, as long as you have some sort of template/jig to assist you placing them. And of course, you are VERY careful as you place them - they will want to flip over onto their neighbours, until they are flat on the steel plate.
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