The Wind is Free!

I am thinking of using a continuous coil of wire, with the wire bent in a square wave pattern, all around the stator.

I am thinking that this will essentially be the same as using individual coils, yet will use less wire, as it is only the 'vertical' sections of wire which are useful, as the moving magnetic field cuts past them. Common sense says this will also be easier to wind. Any ideas on clever ways to wind / mass produce this shape?

This has been used before ( Google Windspire and have a look at the Engineering and Technology brochure under downloads).

Obviously you would only be able to generate single phase power this way. However what if you produce 3 of these and shift their orientation, so that they produce 3-phase? Care would have to be taken to ensure the phases are balanced though.

Great idea, and yes for a single phase it could use less copper, although I am not sure it will be much less. Perhaps if you post a drawing of the layout it would be clearer?

For multiphase, how do you fit the phases into each other, without either making the stator very fat, or using long connecting lengths between the coils?

This is a picture of a stator from the Windspire brochure, to give you an idea of what I'm talking about.

I am not sure if it is very feasible for multiphase - its major advantages would be much simplified wiring, and hopefully easier construction. If anyone has any ideas of how to wind this pattern quickly and efficiently it would be greatly appreciated. Even if it is not as efficient, sometimes in windpower it is cheaper and easier to upscale rather than optimise, as wind energy is 'free'.

Clever,
The magnets move in and out of the coil, more or less they same way they would with individual coils. The magnets must - of course - all be oriented the same way, and multi-phase is not possible with just one coil.

Wow, looks neat. I can't see an easy way to make by hand though.

Disagree with Greystoke - magnets can be alternate N/S if there is one over each leg of every coil.

Agreed. I was wrong

However . . . . I'm reconsidering that

Hi Greystoke

I also got a little confused but thinking about, you will need alternating N-S polarities. If it was the same polarity per arm, the emf (voltage) setup in each arm would have the same orientation ie. all pointing away from or towards the centre. Now if you summed up the individual voltages over the entire coil, the voltages would cancel each other out. This is why you would want alternating polarities, setup so that one is positioned over the sections of wire in the outward direction, and the other positioned over the sections of wire pointing towards the centre. I hope this makes sense. I guess one could use the same polarity for every second arm, if less magnets were to be used.

I am going to be doing some testing on this design, to try find optimal spacing and configuration for a good voltage waveform with minimal harmonics.

I have been quite interested in home built wind generators, and am currently working on this as my undergrad thesis at UCT here in Cape Town. I am looking to build a prototype with a greatly simplified yet clever design, from low-cost materials. I am planning to see if I can use this stator design to optimise/simplify the design. This project is going to get some exposure from EPICS (Engineering Projects in Community Service) and hopefully some good exposure for wind power in general in Cape Town.

Windgat, as you've done all this before I'd greatly appreciate your opinion or help I am living here in Rondebosch

@justLV
How would you orient the magnets ? N/S through the plane of the coil, or N/S pointing to the centre ?

N/S through the plane of the coil, like a normal rotor. Was a bit ambiguous...

Hi justLV. Sure, if we can work together on some stuff that would be great. As a start, I do think there is an advantage to multi-phase...

Thanks, I agree. Ya, three phase definately has its advantages for all power systems...

However, the point of the project is to use low-cost or scrap materials - I already have about 20 harddrive magnets which i am going to cut, though they will all have slightly different strengths. With a three phase design, you will have to ensure all the phases are balanced, which will be difficult if the design is to be built with scrap components. This single phase design however, gives a lot of leniency, even allowing magnets to be added as they are sourced, which I guess would be ideal... Just an idea

Yes, a good point about single phase and scrap magnets.

I think I could get a few more HD magnets if you need them.

Thanks, that may really help me out. I have already sourced quite a lot though.

It turns out that this called a wave winding, and it seems that people have had quite a lot of success with it, even by using it for three phase power. The stator seems to work quite well with testing, so I think I will start trying to make it soon...

Ok, so I've done lots of FEM testing of the magnet setups and it turns out that HD magnets, as they come, produce very desirable magnet flux. It has to do with the fact that the two oppositely oriented halves, create a better pathway for magnetic flux than a normal magnet. I will post some of the testing results soon. The stator however has to be perfectly aligned to the magnet spacing, which can be done quite easily with this winding. I was hoping for these results, as having to cut harddrive magnets in half is a step that can make this generator harder to construct by people with limited access to tools and machinery...

@Windgat I'd love to get a chance to be able to see your rig or get some advice on the mounting of my design if possible anytime... I have got some guys that can help me with casting the stator, so I should be able to do that tomorrow. I'd just have to check and see what type of scale I can make my windturbine. I'd initially be looking at a VAWT for simplicity so there is effectively no limit on the size of my stator. I apologise if this post seems out of context of the title!

Sounds interesting. Sure, email me on peter AT windpower.org.za and we can make a plan

Hi JustLV - I am also in Rondebosch and doing the course with Peter.
Would it help you to get a batch of hard drive magents from identical drives?
I may be able to help you out here....

In terms of winding it: If you use a board with pegs / dowels at the correct intervals, you could wind it around them might look a bit more square than round, but you'd be able to layer it more or less neatly... I'll try to post a diagram of what I mean...
J

Thanks Paul, that may be a great help. At the moment I have made a prototype with some harddrive magnets which seems to be working out quite well, yet I think it could be great to attempt my design on a larger scale if it works out...

Thanks JurgenKahle, I agree with your idea. The fact that it is square shaped would not be detrimental, as an emf is induced perpendicular to the moving magnetic field, so only the perpendicular length of wire is important. I was thinking there would be some quick and easy way to start out with one large coil and then "press" it into shape, yet it may just be easier to do it the long way

Justin, I just had a thought. Since we spoke yesterday I've realised that my idea of a "peg-board" for your continuous coil is flawed.

The first "layer" of turns is no problem, since you put one turn above the next. The issue happens from the second layer. The wires would cross on the path where the flux cuts every time! The result would be that you'd have a really fat middle on every up / down bit of your winding and would run out of space soon. Very impractical.

Conclusion, you would probably have to go with your idea of bundling the wires first and then bending them into the shape you want. Question is, how would you bundle them and keep them in one continuous piece?

Regards, Jurgen

Ya i think i will bundle them all together, and mark off where I want to bend them with masking tape.

BTW Found this site which shows some people who have done something similiar - incorporating three phases even. http://www.fieldlines.com/story/2008/11/27/211427/37

I suggest to keep the bundle together with cable ties. Tape produces too much resistance.

Do u mean resistance to bending the wire? I was thinking in electrical terms, so I was obviously confused... Cable ties would take up lots of space on the stator though which would be non-ideal though...