Wire Quantity Question

[kevindtimm]

I want to wind some test coils for a small (7") rotor using HD magnets (some of you will probably remember my feeble queries from a couple of weeks ago).

I have two questions.  How much wire (in weight) should I expect to use in a single coil?  This, of course, prefaces the second question,  how many turns I should wind?  Through reading other posts, it seems that 20ga wire will be OK.  I'm creating a prototype and the fact that it works is far more important than how much - or little - power it creates. The magnets will be decent sized (I got some 1/4" thick monsters and I'm doubling the others to be the same size).

[wdyasq]

I believe you are asking for a volume of wire. As a coil has 3 basic dimensions and a hole approximently the size of the magnet, let us see how many we have from the information provided.

Well, we don't know how many magnets will be on this device so even the 7" dimension is pretty useless. No diameter of coil, no thinkness, no airgap to guess the thickness.

Sorry, I don't guess I am smart enough to read folks minds. Maybe if folks posted enough information they could be helped.

Ron

[Stonebrain]

hi

Hi kevin,

For designing your generator I propose the following procedure:

1) you choose to make an axial fflux dual rotor 3phase alternator.

   if you don't understand the basics,do some reading on this board

   until you grasp the basic principles.

2) depending on the magnets and steeldisks you have you design your

   magnets rotors.For a small generator choose 8 or 12 poles.

3) present your design on the board and ask what airgap is recommended

   and what power you can expect.

   flux will answer you.Allways listen to flux.

   Now you know the airgap needed and you know the space availabel for the

   coils.Now you know roughly the amount of copper you can put in it

   but you know nothing about how many turns and ga

4) Make a test coil to determine the relationship between rpm and

   volts/turn

5) Now it's time to think about the blades.

   Think about what windspeed you want cutin.

   there is a complex relationship between the voltage/turn tsr and diam

   of the blades.ask for advise.

   flux will give you good advise about the blades you need for

   your genny.

   Now you will know rpm of cutin,wich determines turns/coil

6) With the number of turns/coil and the space available for the coils

   you can determine the ga of your wire.

you see,it's simple

Good luck!

cheers,

stonebrain

[tecker]

es more information is required for good feed back starting with your needs ,

or scale what your trying to power in watts ( rough guess) and start there.

If you need some faround materials cut down a couple of microwave transformers .They have the least amount of varnish on the coils just don't nick the coils when your cutting .If the wire was varnished and sticks when you pull it off  roll it out straight and test by putting power on the wire and run a probe up and down the wire slowly . Any thing suspect paint with coil varnish Or spar urethane ( not rated for 155 or 200c but for moderate duty this works well). To take the kinks out run the wire loop[ half way around a wood dowel and smooth it out testing after .It's not a bad idea th paint it any way after straightening . A finished product you want to last should be constructed with 200c wire to deal with over amping and heavy loads.

[ghurd]

With 7" disks and HD magnets, 16 poles should fit nice.

The deeper they are stacked, the better the chances it'll work!

G-

[finnsawyer]

Take the weight of the copper you have available and divide it by the number of coils.  That's the maximum amount of copper per coil.  Wind one coil with that amount of wire.  You might want to stop when the total width of the coil is twice that of the magnet, as that seems to be the relationship that is used for a 3:4 alternator, and no one has stated otherwise to my knowledge.  That restriction wouldn't apply for my 3:2 design.

[kevindtimm]

Sorry, not enough info.

I have 24 mags, 12 to a rotor.  They are ~ 1/2"W X 1/2"L X 1/4"depth.

Depth of coil, not sure, I'm trying to figure that out too

[kitno455]

ARG!

[kevindtimm]

1. I will indeed do a three phase
   
2. I have 24 mags, so I'll do 2 disks of 12 magnets each
   
3. Not quite sure I understand, how much info is necessary to have a 'design'?
   
4. I'm having a heck of a time finding mag wire locally, and so am trying to get info about wire before buying any.  This makes it hard to wind a test coil.  If I wind one with 21awg, how will it compare to 20awg (for example)
   
5. ok, when I'm there, I'll ask
   
6. Since all three items vary with each other (turns, space, gauge) I'm trying to find a way to do this without buying items I won't need going forward
   

[kevindtimm]

(yes, I know the fin-history)

[RP]

The test coil is to determine volts/turn only so it won't really matter what gauge it is since there won't be any load.  You could do a test coil with 12 gauge or 30 gauge.  It won't matter.  

Once you know how many volts you get per turn at your target cut-in rpm, you'll use that to determine how many turns of your "real" wire you'll need.  Knowing that and how much much space you have (width and airgap), you can figure out how large a wire gauge you can fit with the needed number of turns to get your charging voltage at cut-in.  You'll want the thickest wire you can fit to minimize resistance.

Knowing the wire gauge, coil dimensions and the wire gauge you can calculate the weight of copper and then add 10-50% depending on how confident you are.  :-)

Hope this helps

[kevindtimm]

That's a huge help, thanks for that.

BTW, I'm guessing I'll be pretty good at winding coils since I did this for a job quite a few years ago at a company called Power Conversion Products in Northern Illinois (Crystal Lake).  We made the biggest hand wound transformers you've ever seen for battery chargers in Nuclear Plants (the battery chargers were as big as 4' X 6' X 6' (W x L x H)

I was always good at winding (and the math necessary to find out if the coils were going to fit in cores) but never did QA.  I'm kinda surprised I didn't remember what you stated, but I sure remember it now!

Thanks again.

[finnsawyer]

I took a look in the FAQs section.  I didn't see anything about building 3:4 alternators.  Instead of criticizing me why don't you people put together a FAQ section to help newbies design and build their alternators.  As far as my comments are concerned, they are true to the best of my knowledge, whether you like it or not.  If you can show that I'm in error, fine, otherwise keep your peace.  Just disparaging something because it's new serves no useful purpose.  My thinking also evolves over time, and I have concluded the most realistic test of the two designs would be to use the same number of identical magnets and the same operational resistance, which means for my 3:2 design that the wire be three times greater in cross sectional area.  This means one third the windings per coil, but keeping the coil dimensions the same.  Why?  With the 3:4 design the resistance of two thirds of the coils is seen, while with my design having twice the total number of coils, the resistance of all the coils is seen.  So, with one third the number of windings per coil, twice the number of active coils, and twice the rotor diameter there is a good chance my design will show a greater voltage for a given rpm.  The cost of the two alternators will be nearly the same.  Anybody care to try it?  

[Stonebrain]

 " Not quite sure I understand, how much info is necessary to have a 'design'?"*

You have your design if you know diam of steeldisk,number of poles,kind of mags.

You're there allready.Can be usefull to make drawing,but I guess some do without.

If you magnets are hdmags you have to cut them in two because they have

an opposite polarisation on the two extremities,then you put two together

when putting them on the disk.(youcan stack them on top of each other too)

I don't know the airgap you need.Others can advise you if you clearly present

your 'design'.

cheers,

stonebrain

[Stonebrain]

Reading your earlier comments I see that you have 1/2' x 1/2'x 1/4' mags.

If you do a search for 'airgap' on the board you maybe will find indications.

[kevindtimm]

Just so I can join the family, I submit the following:

Please build it before recommending it to anyone else.

[kevindtimm]

<quote>

If you magnets are hdmags you have to cut them in two because they have

an opposite polarisation on the two extremities,then you put two together

when putting them on the disk.

</quote>

I understand that I have to cut them in two, but I hadn't thought about the second part.  I assume you mean, cut in two, flip one half over and glue them down.  That's a very nice solution (and it will give me approximately 1" X 1/2" X 1/4")

Thanks.

[ghurd]

See stories by 'Dastardlydan' about his 'hurricane' from HD magnets.

http://www.fieldlines.com/user/dastardlydan/stories

G-

[kevindtimm]

Lots of good info, thanks.

I especially liked the other contributor who stacked mags about 3-4 high to get (as he claimed) some pretty significant power.  I love people who do it with what they have, not always with what they can buy.  3 or 4 of these gennies could be very interesting.

[finnsawyer]

Since I don't want to build two alternators due to the high cost of magnets, I am looking for an existing alternator that has been built and evaluated that I can use as a standard (yeah, I know that's dubious too, but it's better than nothing).  I prefer one using circular magnets one inch or less in diameter.  Anyone wishing to provide info on their alternator can post it to my diary.

[finnsawyer]

I find the title of your comment rather interesting.  Just what untested theory are you talking about?  The design of my alternator is based on Faraday's Law, which has been thoroughly tested over many years.  A little explanation would be helpful.

[kevindtimm]

OK, I'll bite.  Well, not really, just to regurgitate what's already been suggested.

Before ideas are foisted upon the general populace, it's common to build something that supports these ideas (say, Hugh Piggot as an example), no matter how theoretically sound it may seem to be.  Everyone here (it seems to me) is very interested and excited about wind power.  The caveat being that nobody seems to have a large amount of spare time or money.  So, at least for me, I would be heartily disappointed if I built something only to find out that I'd invested a large amount of time and money and it worked worse than a proven design.  Especially if I found out that it cost me either more money and/or time than the proven design.

Hence the unproven theories title.

[finnsawyer]

I see you still don't get it.  The fundamental theory here is what happens when a magnet moves past a coil.  The action or result is the same for both the 3:4 design and my 3:2 design.  The way the outputs of the coils are combined, or the configuration, is different.  That violates no existing theories.  The reason I felt I had to flag this (I really don't care what you think) is that your title made it look like the design was based on some off the wall theory (like the Bedini motor?), which it is not.  Anyone can decide for themselves if they wish to try the 3:2 design, but their decision will not be helped by implying that the design is based on some unknown theory.  It is obvious that you do not have a clue how these permanent magnet alternators work.

Here's a question for you:  What should a person who has ten high quality magnets do, if they wish to build an alternator?    

[lohearth]

  Buy 2 more

[lohearth]

 Or build single rotor and have 1 spare

[finnsawyer]

As you realized he would need eight or twelve magnets for the 3:4 design.  With eight magnets he needs six coils only four of which would be producing output voltage at any time.  By going to my 3:2 design he could use all ten magnets for 25% more flux.  He also uses 15 coils ten of which are producing output voltage at any time.  Not only that, the magnets are moving faster past the coils due to the larger rotor, which gives a larger output voltage per coil.