How to connect coils

[Other David]

Hello is it possible to connect coils as individuals, connect each coil to a rectifier then to a heavy bus bar around outside of coils for DC voltage. Thank you
David

[SparWeb]

Yes you can.  It becomes a "rat's nest" or wires, be warned.
There are reasons not to do it, though.  When there's current flowing in a coil, it pushes back on the magnet generating the current.  That leads to a "cogging" feeling that resists turning.  If you have a bunch of coils resisting movement at the same time, our generator will turn in a halting way. 
With all of the wires out of the alternator individually, you can still connect in a 3-phase fashion.  Or some other combination that you choose.  The cogging will be just one of many effects that re-connecting groups of coils will have.

[Other David]

Hello sparweb thank you for your reply I think I understand what you mean by clogging but I was still going to use less coils to magnets to prevent this. I'm of the understanding that you can mix multiple DC supplies into one DC being more forgiving than AC. What's in my mind when you do coils in three phase you may have three or four or five coils connected one after the other creating greater resistance. Individual coils I'm hoping will produce less resistance to thin copper could be used saving me money. If anybody knows of information of people doing this could you point me in the right direction please something for me to consider before I start building anything.
Thank you very much
David

[Adriaan Kragten]

The disadvantage of rectification is that you get a voltage drop over the rectifier diode which is about 0.7 V for silicium diodes. If every coil is rectified separately and if the DC currents of different coils of one phase are added, you have this voltage drop for every coil. If all coils of one phase are connected in series and if a 3-phase rectifier with 6 diodes is used, you have only a voltage drop of about 1.4 V because for star rectification, the current flows always through two of the six diodes. This voltage drop is relatively low if you have a nominal battery voltage of 24 V. The power loss in the rectifier is the product of the voltage drop times the DC current. Rectification of a 3-phase current is explained in my public report KD 340 for star and for delta.

[Other David]

Hello Adriaan thank you for your reply I've looked at your report and my head hurts in-depth detail a bit much for me I'm afraid thank you all the same.
David

[Bruce S]

There was a Very well know member here that built what you are referring to "Jerry" came up with "Jerry Rigged"

Here's a post that should help you, quite a few well respected people responded to this post, including Jerry, Tom Wooferhound and Hugh Piggot.

https://www.fieldlines.com/index.php/topic,140560.0.html

It should help.

Cheers
Bruce S

[Other David]

Hello Bruce S thank you for your reply. I've looked at the link provided but not covering what I'm looking for. I realise using a rectifier for each coil would cost me voltage, if it's possible to make the coils out of thin wire due to less resistance would this brings the magnets closer together increasing flux, possibly increasing efficiency. Three phase arrangement requires three possibly four or more coils to be connected to make one phase increasing resistance, what I'm trying to find I think, is will individual coils increase efficiency and make For loss of votes in rectifiers.
Thank you very much
David

[taylorp035]

Hi Other David,

I think how you hook up the coils is a question of how flexible you want the generator to be in the future if you decide to change the configuration of the wiring.  I've many times had the two leads from each coil exit the stator and then configured the coils in series or parallel depending on the voltage I was trying to achieve.   I think the only real planning you need to do is pick a number of coils that suits the possibilities that you may entertain in the future.

So for example, if you are doing a single phase machine and you have 6 coils, you can wire them 6 in series, 2x3, 3x2 or all in parallel.  The single phase will have the most noticeable pulsing since your output will be one giant sine wave.  I've done this series/parallel thing on both a single phase 6 coil machine and a 12 coil 3 phase machine.

There are two kinds of pulsing and cogging that can occur.  One is from the rising and dropping load that the alternator is generating, which generally isn't too much of an issue with an axial flux alternator (highly suggest you make one of these).  The other kind of cogging is when a magnet gets near a piece of iron.  This is generally only an issue if you decide to try and have iron or laminations in your alternator... a good example of this would be any brushless hobby motor for a rc car or plane or a servo motor for a machine.  This cogging can be quite high and be challenging to overcome with just the torque of your blades.

I wouldn't recommend adding a single phase rectifier to every coil since you will loose 0.7-1 volts, which can add up to a significant amount for just about any reasonably size alternator for a windmill.  You might be able to get away with it on a very high turn coil with thin wire, but you would be much better off wiring it up in the typical 3 phase star pattern.   3 phase bridge rectifiers are fairly cheap to buy compared to the wire and magnets.

[Other David]

Hello Taylorp035 thank you for your reply very interesting. I am thinking of axial flux alternator. I have come across individual coils cast in there own resin with screw connectors to connect them, I can then do the same as yourself experiment with different ideas and connect the coils as I please. Hugh Piggott designs has been around for very long time now and many many of them built with so many minds working on them something new and worthwhile may have come from this. Hopefully find different ideas that's been tried before I build anything other people's experience is worth a lot.
Thank you very much
David