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434josh
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Joined: 13/06/2012
Location: United States
Posts: 10

Posted: 04:17pm 30 Aug 2012

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HI to all!

I am starting a build on an Axial Flux wind turbine to help power my home and/or heat water. I purchased Hugh Piggott's book on AF motors. I have read it over pretty well and know I can build these with ease.

I do have a few questions as my build isn't exactly illustrated in his book.

I purchased blades and they are 3.3m where his book uses 3, 3.6 and 4m. Would the instructions for the 3m work ok or would I need to use the 3.6? Somewhere in between?

He suggests 9 coils and 24 magnets for the 3m and 12/32 for the 3.6m. I understand that the coils must be divisable by 3 to produce 3 phase however what do the number of magnets have to do with the output? They have to be an even number but what would happen with a higher or lower number?

Hugh recommends N40-N42 magnets, would stronger magnets be better or counter productive and why? He suggests 46mm x 30mm x 10mm (1.81" x 1.181" x .394") where I can buy 2.0" x 1.0" x .500" in N42, N50 or N52. Which would be best? Or would 2 x 1 x .375 be better?

I want to gain as much knowledge as I can prior to starting the build so I really appreciate any help or experiences you guys/gals can offer. I work in a major aerospace manufacturing company which I love however I really wish to help bring renewable energy sources to more people, people who want to be green but cannot afford the cost and do not have the ability to build their own. I would like to build generator motors in various sizes and outputs and make the available at an affordable price if I can build them well and functional enough to make them worth while. Hopefully the market is there as I think it is.

Downwind

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Joined: 09/09/2009
Location: Australia
Posts: 2333

Posted: 05:45pm 30 Aug 2012

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Sooooooooo many questions.
Sooooooooo few answers.

The bigger and stronger the magnets the greater the power produced.
Shape of magnets is also a factor, most here like the 50mm round magnets and not the rectangular ones, the round makes winding coils easier and tend not to burn the stator up as much as the rectangular magnets.

As for a supplier you could try " www.rishengmagnets.com " they will sell in small quantities and there is a few threads on the forum from them if you search.

M50 is the better magnet as the "M" and "N" is the temperature rating for the magnet and needs to be high enough, as once exceeded the magnet will not recover, a lot of heat can be generated in a AF mill.

3m blades is that each blade length or the diameter of the blade set.

If you want to give good advice to others on RE power and save money the best advice is to buy solar panels, as they are guaranteed to give a return daily and wind is not, also the cost of solar is less than the cost of a mill, it also is a static device with no moving parts making it much easier to install and less risk of failure.
Ask anyone here who has been involved with wind for some time and they will tell you the same, even though we still fly mills, it more for the challenge than the returns.

Pete.

Sometimes it just works

434josh
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Joined: 13/06/2012
Location: United States
Posts: 10

Posted: 01:51am 31 Aug 2012

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Thanks for the reply.
Solar can work for me however most people won't sacrafice the space needed for panels. Plus in my area, we get hail 2-3 times per year and they are without warning. Panel damage would be unavoidable.

Is there a chart available for the number of magnets and size/shape/number of coils for the round magnets? What thickness on the 50mm rounds?
Must the magnet plates be made of steel? Does the steel serve a purpose other than helping the magnets stick?

To answer your question about blades, 3.3m diameter, not each blade.Edited by 434josh 2012-09-01

Tinker

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Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 03:40am 31 Aug 2012

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There was a chart regarding the ratio of numbers of magnets to the number of coils, unfortunately last time I looked the site up it was no longer available. It was in German language anyway (which I can read) and I still have a copy of the info on ratios.

Anyway, some magnet/coil ratios work better than others and for some the coils have to be connected in a not so straight forward fashion.
I strongly recommend you stick to the ratios given in Hugh's instructions, they are proven working solution. Start experimenting with these ratios after you built a number of wind generators if you must but not for your first attempt.
Good luck.

Klaus

434josh
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Joined: 13/06/2012
Location: United States
Posts: 10

Posted: 12:32pm 31 Aug 2012

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What about the magnet plates? Can they be aluminum alloy in lieu of steel?
Could N52 magnets make up for the blades being 3.3m in lieu of 3.6m? I am not sure which plan to use, 3000mm or 3600mm.

Downwind

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Joined: 09/09/2009
Location: Australia
Posts: 2333

Posted: 05:43pm 31 Aug 2012

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As it would appear you have no idea of what you are really doing in any way i think best you stick to the book you have 100% of the way, because if you change 1 factor all the other factors to the design changes as well.

Think about your question on magnet plates......now they are called a magnet plate which would give a hint the magnets need to stick to them, and unless you know something we dont then aluminum alloy wont work.

You could use aluminum alloy with a steel insert for the magnets but those who have done that comment its not worth the effort for a small weight reduction.

If you change the magnet from what the book says then all your turn ratio for the coils will change too, best to stick to the book i think till you fully understand what it is you are doing.

Sometimes it just works

434josh
Newbie

Joined: 13/06/2012
Location: United States
Posts: 10

Posted: 11:00am 01 Sep 2012

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Downwind,

Yes I fully understand each change affects other aspects...that is the point of my post. I am asking if anyone has already done this or can speak to the exact affect I will encounter.

The reason I was asking a out the magnet plates made from alum vs steel was for heat dissipation, nothing to do with weight. It can get quite hot where I live, up to 115 degree F. Its currently 101F according to my home weather station. I can mill pockets for the magnets to seat into and either epoxy into place or use the magnets which bolt into place. I wanted to make sure the steel wasn't important to the magnetic field in relation to the coils.

I appreciate the comments and hope to see more.

Perry

Senior Member

Joined: 19/11/2009
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Posts: 190

Posted: 03:43pm 01 Sep 2012

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Josh,
You must use steel for your magnet plates. They are an essential part of the magnetic circuit. I have the same book which I purchased before building mine. Take your time and read through it completely. Read through it twice if necessary. I did.

The questions you are asking are all explained in detail there. Aluminum will not dissipate heat at a greater rate than steel anyway so there is nothing to be gained in the first place. Except weight of course.

Perry

434josh
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Joined: 13/06/2012
Location: United States
Posts: 10

Posted: 03:50pm 01 Sep 2012

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Thank you for answering my question Perry.

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