How many magnets versus coils

[chewyms]

  I have been doing some research on building a wind powered generator.

I've noticed that some have the exact number of magnets versus coils and some are not.

Is there any things that should or not be done for this.

I've always thought that the number of coils should match the number of magnets.

Thanks for any feed back.

[Nando]

For wind mills there are two types of arrangements:

Equal magnets and coils; this case the generator has cogging that may require certain higher wind velocity to start operating

The second case where the magnets have a EVEN value and the coils are ODD (one less than the magnets pairs).

Like 24 magnets (12 pairs) and 22 coils (11 pairs) for minimum cogging effects which allow to start with low wind velocities.

The second case may give a distorted wave form that for battery charging does not affect the end result.

Regards

Nando

[edy252]

hi....

to connect ur coils in series or parallel (usual connection single phase) u need equal nubmers of coils and magnets.....while, for 3 phase, which is much better concerning battery charging, smooth starting, and less wire losses, u need a certain ratio between the number of the two.....

i do prefer 3 coils for 4 magnets

ex:

3. COILS / 4 MAGS
   
6. COILS / 8 MAGS
   
9. COILS / 12 MAGS
   
   

AND SO ON

[DanB]

The comments regarding cogging and startup torque would only be true in this case if its a machine which has cores in the coils, or slotted laminates.  A single phase machine, same number of coils as magnets, will not cog otherwise, untill current is flowing - so no matter what number of coils you use, startup torque is not an issue if it has not cores in the coils, and/or no slotted laminates.  If its the "normal" dual rotor design... startup will always be a none issue no matter how many coils you run with.

If you run with same number of coils per magnet that'd be single phase.

Half the number of coils as magnets would also be single phase.

Single phase seems a bit simpler and there may be a bit more flexibility in how you can wire it up, - that's where the advantages end though.

3 phase will run with much less vibration once current starts to flow.  It will make better use of all the conductors both inside, and outside the alternator, and in the end you'll squeeze a bit more power from your machine if you wind it up 3 phase.  A simple and effective formula is 3 coils/4 magnets.  There are some other interesting winding ideas from windstuffnow that may be more effective for 3 phase output.

Do a search on this board if you want gobs of ideas and opinions and a good way to get even more confused!! ;-)

[devoncloud]

If you will look at windstuffnow's postings, you will also see that you can make three times the amount of coils than you have magnets.  if you have twelve magnets, you can have 36 coils.  the coils simply overlap each other a little.  Doing it this way puts much more copper under each magnet causing you to get much more power from your unit than if you simply made twelve coils for twelve magnets or whatever.  

So I guess the answer to your question is that you have a good number of choices.  It all depends on how much research you want to do.  Everything that you will need is on this website just about.

Devon

[devoncloud]

oh ya, making a bunch more coils like windstuff now also prevents the cogging affect in single magnet rotor designs as each magnet is always under a load.

Devon

[hvirtane]

Some of my design ideas

you can see in my diary:

http://www.fieldlines.com/story/2004/6/2/163021/1860

- Hannu