Coils

[Murlin]

I searched the Forum and found some info on this but wanted an entry in my journal.

I was researching coils and have been reading that flat wire might be better.

A lot more research needs to be done, but I can say from what I am reading, flat wire would work pretty darn good especially if one uses multiple wires in hand.

Could you wind a coil without crossing over at all....perhaps?  I dunno....

There are manufacturers that just flatten out the round wire somehow without damaging the insulation.

So like 6 in hand for a .625 stator would be perfect for wires that were flattened to .1 wide....

Cant wait until I get my rotors on the fame so I can start doing some testing.....

Since Samo said that I must build my stator to work best at 23 MPH, does this mean that I want to be producing my desired max watts at this speed?  I am not sure if I understand the significance of the 23 MPH.

From what I gather with all the formulas....

Air density in my area is around .9.  So I can take 10% off the numbers in the Wind Section know what to expect.

If a 20' Genny can produce 7800 watts in a 20 MPH wind, then the rule of thumb is, if I understand it correctly, we can only harvest about 60% of that on a perfect machine about 4800 watts.

Since we can't build a perfect machine, lets say that we make a pretty good one that can harvest 60% of that 4800...which is about 2800 watts in a 20 MPH wind on a machine that works at 60% capability and - another 10% for air density...

So I can expect to get about 2500 watts from mine at 20 MPH if it works @ 60%.

Is that right or am I off in let field as usual??

Someone put meh back on course if I am please

Murlin

[Flux]

For a 20 ft rotor, 2500W at 20 mph will be good going.

It should be possible but it largely depends on the method you use to match the rotor to the alternator.

It comes to a cp of a bit over 0.2 allowing for your air density. If you can hold that over a significant range of wind speed you can consider it a good result.

Flat wire looks attractive but may not prove easy to use. You may find a combination of width and thickness that satisfies the thickness and number of turns of your coils but it does reduce your choices.

This again may be influenced by how you match the rotor. There is not a lot of point in wasting lots of time and effort if it means stall and the need to add resistance.

If you can use the extra efficiency then it may be time well spent.

Flux

[BigBreaker]

I just posted about using flat wire AKA ribbon, made from copper flashing in my diary.  I searched for posts on the forums and found two encouraging ones.  I think ribbon wire is just a bit too much of a specialty item for many people to have access and experience with it.  If the flashing concept works it could make for cheap, tight coils that handle plenty amps.

1 inch of 16 oz copper flashing has 36% more cross section than 3 in hand 14 gauge wire and is about equal to a single 3.5 gauge wire though much easier to wind.  For the record that weight of copper, 16oz, is .0216 thick and measures .00022 ohms per ft.

[SamoaPower]

Murlin,

For further explanation of the energy peak issue, see:

http://www.fieldlines.com/comments/2006/6/26/12214/2424/31#31

Ah yes, coils, another one of my favorite topics. Probably the single most important factor in obtaining reasonable alternator efficiency is low coil resistance. Any efforts made toward this end will pay off.

In designing my coils, I had an ulterior motive in that I wanted the coils to also serve as structural elements in the stator. Improved cooling was the main reason behind this. Consequently, I wanted the coils to resemble a solid block of copper as much as possible. Toward this end, winding density is all-important.

I think it's generally accepted that square wire of reasonable size can produce the highest winding density, without eddy current issues, if properly done. It's a bit tricky to handle so a winding machine is definately desireable. Another requirement for high density is to eliminate crossovers in the winding process. This dictates having a single turn per winding layer.

It works out that 7 in hand square #14 produces a coil a little under 1/2" thick which is what I was shooting for. A little research showed that square, self-bonding #14 is available. The self-bonding feature is where they apply a heat setting adhesive over the wire insulation and the coil is baked after winding to activate the adhesive, bonding the whole structure together. Now, if I can just find a supplier that will sell 70lb to me at a reasonable price. If you find one, let me know.

Other than using solid silver wire, the above produces the lowest resistance coils for the desired volume and shape factor that I could come up with.

[terry5732]

Although you are filling the coil well, I think you are talking about 'stacked' turns in which your outer winding is significantly longer than your innermost winding. And then you have these tied together in parallel? Dunno the ramifications there.

I have tried a number of 'flat' windings and got zero output. I sat and cut aluminum foil into 1-1/2" strips, enameled, meticulously wound, and nada, zip zilch. I think in the broad cross-section the current gets lost eddy style.

[Murlin]

Thanks dude!!!

I have been trying to find Flux's post forever now it seems.  I ran across it once, and then,  could never find it again.  The search engine would not find "Matching the load"...

Murlin

[Flux]

It was in my diary, but nothing seems to be there now. I am no good at finding things here, maybe someone else can find it.

Flux

[oztules]

http://www.fieldlines.com/story/2006/3/17/185646/194

.......oztules

[Flux]

Thanks Oz, must have gravitated to the southern hemisphere.

Flux

[electrondady1]

 this is the first time i have heard of self bonding wire .i have been experimenting with two phase / overlaping coils and have had a certan amount of success . the  results would be an almost solid copper stator very little room for resin. this self bonding wire could be usefull . as the coils need to be manipulated to a certan extent. i am not so much interested in square conductors but if the stator could be set up and then baked for rigidity it would be very practical. thanks for the tip !

[electrondady1]

after just a brief search one factor is apperant with self bonding mag wire. the operating temp of the coils becomes a real factor and must be kept low or the cohesion of the coating  is drasticly reduced.....hmm !

[Murlin]

Thanks OZ and Flux......went back and re-read the "Matching the Load" post and I think I will stick to round wires also.  That post is very informative BTW!!! U da man Flux

Looks like DanB saved me the trouble of experimenting with the ribbon wire...So, also thanks Danb....

Murlin...