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Alternator finished | 7 comments (7 topical)

Re: Alternator finished (none / 0) (#1)
by windstuffnow on Mon Dec 08, 2003 at 10:12:47 AM MST

Looks very nice Dan! What was the ohm reading on your coils when completed? To bad the gap came out larger than you wanted, thats going to eat up some power but should still kick out some good power.
I'm designing an alternator to work with a slow turning VAWT. The idea is to have the unit start charging at low rpm's ( around 30 to 45) but produce full power with very small rpm changes. ( full output by 100 rpm's or so) It's been quite challenging and I'm still a bit off for the final product. I'll be using similar magnets ( my smaller segments - which are only 2" tall x 1.57 top ). I may steal your idea using strands of smaller guage wire as opposed to one heavy strand. This may help reduce copper losses by reducing the eddy currents and I believe, not sure yet, I may be able to get more copper in the magnetic path this way. Interesting idea anyway...

Keep us posted on your output data when its together!!!

Have Fun
Ed

Have Fun! Windstuff Ed

Re: Alternator finished (none / 0) (#2)
by DanB on Mon Dec 08, 2003 at 10:59:12 AM MST

Hi Ed - when I hook the meter to it is says .1 ohms (and beeps at me). So it must be somewhere between .1 and .2 ohms/ phase.

The airgap is kind of a bummer, but on the bright side, the cutin speed came out exactly where I wanted it and the stator is a bit stronger/less flexible - which is good I think because it's large enough - and the coils all pretty much touch each other, that weakness in the stator was a concern. It came out this way because I used a bit more fiberglass than normal on both sides, and I heated the resin up a bit much before I started (and mixed it a bit too hot) so that by the time I was putting the top on my mould it was allready setting up. (I should've been more patient!).

Perhaps next time I'll have the resin go a bit more slowly and then perhaps I could get away with slightly thicker wire and a few less windings (maybe 4 strands of AWG 15 wire) so that resistance is a bit lower.

I wonder if, in your case there would be any advantage to using multiple strands (other than that they are a bit easier to handle). Would eddy currents in the copper be an issue with you, since youd be burying the windings inside slotted steel laminations? It seems the laminates might take care of the eddy current losses in your case.

[ Parent ]

Re: Alternator finished (none / 0) (#3)
by windstuffnow on Mon Dec 08, 2003 at 03:01:25 PM MST

Hi Dan,
Just playing with numbers and what you've given in data. I've calculated between 1100 and 1400 watts in a 25mph wind not including any losses... let me know how close I came...
After calculating out the differences in wire sections it actually takes up more space using smaller wire to make up a larger equivilant. I thought it might come out a little more efficient since the air gaps between wires would be more filled in... Fun figuring it out though... back to the bar stock...

Have fun
Ed

Have Fun! Windstuff Ed
[ Parent ]

Re: Alternator finished (none / 0) (#4)
by DanB on Mon Dec 08, 2003 at 05:55:47 PM MST

"After calculating out the differences in wire sections it actually takes up more space using smaller wire to make up a larger equivilant."

Hi Ed.. I have to say, Ive not calculated this - but if we ignore the thickness of the insulation, that doesnt make sense to me... it should be the same shouldn't it? Except that - really large thick wire is harder to wind tightly, so I actually tend to think the opposite, It seems I can squeeze in a bit more copper this way, but I could be wrong.

[ Parent ]

Re: Alternator finished (none / 0) (#5)
by Jerry on Mon Dec 08, 2003 at 06:15:48 PM MST

Hi DanB
I asked this ? a while back. I thought i could get more copper in a coil of the same phizical size it i used smaller ga. wire.

Then the group consencis was. Big wire , small wire the copper amount would be the same. I thought I could squeez more wire in with the small stuf and perelell the coils rather than siries? DA-NO?

JK TAS Jerry

Airheads Page

[ Parent ]

Re: Alternator finished (none / 0) (#6)
by DanB on Mon Dec 08, 2003 at 08:13:58 PM MST

I think it should be the same either way... except for the thickness of the xtra insulation on the smaller wire. In this case - I had to do it, because the thought of winding a coil like this with something between AWG 9 and AWG 10 wire seems daunting - and Im certain Id have had some eddy current losses in the thick wire.

[ Parent ]

Alternator finished | 7 comments (7 topical)

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