Stator winding for 10'

[Janne]

Hello!

After experimenting with a single phase, single rotor axial flux generator, i decided i'm going to need a lot better alternator to prevent the turbine flying away, and to extract the full power capability. You can check some of the story from my old postings.

I'm planning my new alternator to be built with dual rotors. Rotors are going to be diameter 350mm steel disks, laser cut from 8mm thick steel. I'm thinking of using 2" * 1" * ½" N42 magnets, 12 magnets per disk.

For the stator, i have planned on making 9 coils, in 3 phase. I thoght on making each individual coil of AWG 17 and AWG15 wires in hand (1 of each), with 70 turns on each coil. The phases would be connected in delta, to achieve proper cut-in speed to 12 volt battery bank.

What's your opinion, will the diffrent size wiring and/or delta wiring cause any odd problems? The reason for those wire sizes is, that i happen to have plenty of both in hand.

Thanks for reading.

[Gary D]

 Instead of my opinion, perhaps what the Dan's are currently selling(doer's)... would equal 4 in hand #17 wire if my thoughts are correct and many less turns. Gary D.

 http://www.forcefieldmagnets.com/catalog/product_info.php?cPath=22_30&products_id=182

[DanB]

Winding with different gages of wire in hand bothers me - I think you increase the risk of parasitic losses between parallel windings.  When its under load - the voltages in the different gages of wire will be different and I'm fairly sure the 15 gage winding would be busy heating up the 17 gage winding.  I find that even when we use multiples strands of the same gage wire we suffer a little bit from this because the lengths of the strands are not identical.  Delta will also surely have some parasitic losses between phases.

If you have to use multiples strands in hand (which you sort of do with a 10' machine @ 12V) then I would use identical wire gages and I would wire in Star.  With the magnets you describe I think you'd do well to use 2 strands of #14 gage wire and about 36 turns.  (I say that because we've built lots of them and that seems to work well)  You could probably fit two strands of #13 gage wire in there if you wind nice tight coils and still keep the stator down to 1/2" thick.

[Flux]

I tend to agree with Dan. Delta has problems but for 12v in a reasonable wind area it may be good enough. I would stick with star. 4 in hand #17 would be awkward to deal with but should be ok. You may get 3 in hand #15 in if you are careful.

If you don't mind using more rectifiers you could use 10 coils and adopt Hugh's 5 phase winding with about 80 turns of #15. This avoids winding wires in hand but means that you are almost forced to put the rectifier in the air.

Flux

[Janne]

Hi, thanks for your comments. Adding more diodes won't be so bad if it simplifies the stator fabrication. I did some searching about 5 phase systems, but didn't find some basic things about it... first, how can you calculate rectified voltage? Will it be sqrt(5)* phase voltage, like in 3 phase systems where it's sqrt(3) * phase voltage? And how about calculating total current?

My problem is, that the cheapest supplier i found for usable wire sizes, like #13 and #14 gauge would sell them for 29$ / per lb (ouch).

[Flux]

You will be hard pushed to find much about 5 phase. Hugh's plans contain all the practical details but I think you will find little else about it.

Hugh uses 1 coil per phase ( hence the thinner wire). The thing is in fact connected as a parallel 5 phase winding. It has 10 coils per 12 magnets.

The voltage factor for star 5 phase is 1.9 compared with 1.73 for 3 phase.

You could do parallel 3 phase by similar methods to use thinner wire of you could Jerry connect the individual coils. Many options, I can only give you a few pointers here, I can't cover all the options in detail.

Flux