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Shape of coil windings on a axial flux generator Answered

I am making a axial flux wind turbine. I have watched many tuts on YT and researched alot on the net, but there is one thing that is confusing regarding the coil windings: Does the gap in the middle of the coil have to be the size of the magnet? many people do this and many don't, from a engineering perspective, which is better, my understanding is that it is best to make the gap as small as possible, that way you use up most of the magnetic flux. What is the best approach and why?



6 weeks ago

Could you post some pics of what you have so far?


6 weeks ago

No offense but most people just attach a suitable generator to the turbine.
Either a salvaged DC motor, or the assembly from a washing mashine motor.
Some just use car alternators....

Building your own generator is not just a matter of coil shapes, magnets and spacing.
You need to consider things like load, available torque, output regulation, field strength.....
A coil in a generator needs to be sized to utilise the max of the available magnetic flux.
It needs to have the wire in such dimensions that the overall internal resistance is not to high.
After all it makes no sense to build a massive generator aiming to reach 2000W if the wire on the coils creates a resistance that limits the output to just 500W....
You say you watched a lot of videos about it, but did you understand them?
Most of them won't give you any real details on the coil winding or generator design if they created it from scratch.

Just to give you some basic ideas:
The number of turns determine the max possible output voltage.
The thickness of the wire corresponds the max possible ampere it can produce.
Together they restrict what is possible in terms of power and output.
Then comes the fun to decide how many poles and what configuration you need.
For the magnets and coil packs...
The flux goes through the laminated steel.
Means a gap as small as possible for the magnet passing over it would be best.
But as said, the coils can only be of a certain size and diameter to make fully use of the available magnetic flux.
In some cases you even need to consider how the magnetic field of the coils affect each other.


6 weeks ago

I dont really understand the layout you describe, but generally you have to see that the coil cuts the most magnetic fluxlines possible while moving. And i think, with what you describe, the closer to the center the coils are the better in this matter. As both coils cannot occupy the same location in space, the closer the better in terms of how much current is induced in the coils.
However, it may be that this gap is there for timing. Maybe this gap generates the proper like 90° offset in voltage?

Jack A Lopez

6 weeks ago

From what I have seen, it is typical for each coil to have an empty center about the same size, and shape, as the magnets that slide past it.

You say, "many people do this and many don't," but this sounds like weasel words to me, if you cannot be bothered to actually point to any examples, of those who do, or of those who don't.

Also I do not follow what you are saying about, "... best to make the gap as small as possible." As small as possible is zero area, right?

What does a gap with zero size look like? Does it look like a spiral wound coil. I mean, like a pancake, or a flat cylinder, with its volume totally filled with copper wire?

Such things exist, but I am guessing filling up that whole cylindrical volume with turns, is just a waste of wire, adding more total resistance to the coil, but not giving a great improvement in number of turns with changing flux enclosed.