Coil winding - how many turns and how much strands?

[Tomy Torn]

Where I can find some online calculator to math this? Can any of yo give some basic concepts?

[Rob Beckers]

Hi Tomy,

There is a calculator that uses Excel posted here: http://www.nadaparasiempre.com/hobbies/wind-energy/generator/index.html

Most is in German, at the bottom of the list is an English version.

-RoB-

[Tomy Torn]

Thanks! I have few questions:

Tip Speed Ratio at Generator Cut-in 1. TSR (n) 5
"is the ratio between the tangential speed of the tip of a blade and the actual speed of the wind" from - https://en.wikipedia.org/wiki/Tip-speed_ratio - how do I know what to put there (lets suppose that I will use PCV blades from the pipe at start)?

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Width of coil leg 5. Width(mm) 40
it's the wire that is between (connect them) two coils right?

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Airgap 2. Distance (mm) 40 >> max 2x height of magnet
air gap between the magnets?

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Number of Poles 5. Poles (n) 20
it is number of +/- - so its just number of magnets x2?

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Packing density 2. Density(Factor) 1.5
It's the distance between wire in a coil right? Any ide what to put there if fr example I use 1mm wire?

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This calculator is VERY nice.

[Rob Beckers]

Thanks! I have few questions:

Tip Speed Ratio at Generator Cut-in 1. TSR (n) 5
"is the ratio between the tangential speed of the tip of a blade and the actual speed of the wind" from - https://en.wikipedia.org/wiki/Tip-speed_ratio - how do I know what to put there (lets suppose that I will use PCV blades from the pipe at start)?


Tomy, I didn't write the calculator, so I can't really answer the other questions (nor have I tried building a PMG, so far). TSR is one I do know though! It's just the ratio between the speed of the tips of the blades vs. the wind speed.

For HAWT type turbines the usual range is between 4 and 8. The best TSR for a given turbine depends on the blades and the angle that they are mounted at vs. the hub.

The underlying physics is that as a blade moves faster through the air, the wind no longer hits it from the 'front' (i.e. perpendicular), but the angle that it hits becomes the vector sum of the actual wind plus the motion of the blade. Since blades are just airfoils, just like the wing on a plane, there is an angle of the blade vs. wind where the lift-to-drag ratio is optimal. That is the point where it is most efficient. You can work through the numbers, and will find that a specific blade, mounted at a specific angle vs. the hub, will work most efficiently at a specific TSR. That TSR does not vary all that much over a range of wind speeds (in other words, for a really good turbine the blades will speed up linearly with the wind speed, so the TSR stays the same).

This is a very short story of something that has much more to it. In practice, if you're just building something and want to test it, shoot for a TSR of 5 or 5.5 and call it a day. Again, this assumes a HAWT. Things are different for VAWTs.

Hugh Piggott wrote a nice wind turbine design tutorial that works through this in much more detail: 1400

This one is light on theory, but heavy on design: https://www.scoraigwind.com/pirate%20oldies/Hugh%20Piggott%20Axial-flow%20PMG%20wind%20turbine%20May%202003.pdf

Here's one about designing PMGs: https://pureportal.strath.ac.uk/files/68123828/EAWE2017GL_Paper.pdf

Hope this helps!

-RoB-