8 Strands of #20 VS. 2 strands of #14

[s4w2099]

This coil is only 45 turns with 8 strands of #20. The thing was supposed to come out squared  but it started to round off after a few turns.

I am wondering if using two strands of #14 will produce the same coil size??. This size is out of the question for me because I am using 11" rotors and this coil came out to be almost 4" diameter.

My target is a 12V system with very low resistance from 30-45 turns of wire. 2x1x0.5 N50. 2.7m diameter propeller TSR 7.

Any ideas?

[hiker]

if the hole is the size of the mags---you will have some loss there--being that the legs are wider than the mags..make a few more test coils tell you get it right..

or google search the board-[coils]

[s4w2099]

Yeah. I know this coils is absolutely out of the question. So far Ive been able to cramp no more than 50 turns of 5 in hand 20 gage. That makes a resistance of 0.069 ohms per coil.

I think it is still very high for a 12V system right?

[s4w2099]

By the way, this will be a 12/9 with 0.5" thick stator (I hope).

[SamoaPower]

I think your main problem, judging from the picture, is not nearly enough winding tension. With that much wire, it takes a lot of tension, perhaps a few hundred pounds, to get a good lay. It's also why you don't have a more rectangular shape.

http://www.fieldlines.com/story/2006/10/21/61110/798

It should result in a coil a little over 0.5" thick and a leg width of about o.8".

Did you twist the wires together before winding? If so, there's no hope in getting a compact coil.

The picture also shows it to be somewhat scramble wound rather than layer wound. That'll give you a lot of air space internally.

It takes a fair effort to get a tight coil, but it's worth it.

[s4w2099]

I didnt twisted them together. I thing is that I did not used that much pressure. I think I only used about 25 pounds rough estimate.

Thats a very nice way to wind the coils. I will have to give it a try. It must be very time consuming. Your overall coil size is much larger than what I can fit in my stator. Ive started to make this stator already with 5 in hand 20 (equivalent to one #14 + one #20; or two #16 in hand). I will finish it and make another one with a similar coil winder as yours. This one should provide well for 30-45 amps. I have more than enough #20 to do it, and lots of time in my hands.

You must be producing monster power with that I guess.

:-D

[Flux]

From the look of your inside turns it looks as though you used no tension at all.

With extreme care you should be able to get it smaller with 8 x#20 than with 2 x#14 but winding more than 3 in hand becomes a complete pain if you want to aim for layer winding, it will take you hours per coil ( only you can decide if it is worth it).

Why do you want 45 turns for a 12v alternator. 30 should be more than enough. If that is the one you want to use the boost converter on then 20 is more like it. ( if you must try a boost converter at 12v then use the 3 inductor version with fets in the bridge).

With all the care in the world you will not reduce the coil size more than about 30%.

Flux

[s4w2099]

Sounds good. I finished my boost converter that I was talking to you a bout the other day, thats why I am rewring. I have plenty of 20 so I will try many stators on this one.

The boost converter worked so nice that I will even try the stator with 20 turns as you say. I will try from top to bottom. First the one that I am winding 45 turns per coil, then 30 turns, and finally 20 turns.

I might even go with fewer turns than 20. My boost converter starts to work at 7.5 volts. So I should get optimum TSR whenever the output voltage hits 7.5 volts DC.

I have no particular reason to be using 12v so maybe at the end I will be satisfied with using the 45 turn stator to charge 24V bank with the boost converter.

The last stator that I made 60 turns of 3 #20 in hand jerry connected I was able to see around 500Watts in a stormy day (I have very turbulent wind). I noticed that resistance was actually keeping the current from swelling. Thats why now I am aiming for lower resistance. I dont complain about 500Watts I dont need more but I want to see what happens if I go even lower.

That was PEAK power I want to see if I could get to 100W RMS.

[s4w2099]

Ok, I am testing the new stator. I ended up with 42 turns of #15 wired in star. Before I had 60 turns of 3 in hand #20 jerry.

Now I reduced the airgap from 1 1/8th to 1".

Before when I shorted the leads the blades would stop in less than one second even if turning at 200RPM. Now they will stop fast but not as fast I would say 5 seconds.

Other thing I have noticed is that when I load the mill with a 0.5 ohm resistor the speed will start to drop gradually and will sustain more current across the resistor for 30 seconds or more. Before with the same resistor it will come to a fast halt.

Now the cutin is at about 140-160RPM. I have not seen more than 900mA. This is at about 7 - 9 mph. Dont know how good is that.

I got tired winding 5 in hand so I will get two #14 to make the next stator.

Question:

Could the resistance still be too high and thats why the blades dont just STOP fast when shorting?

The resistance is way lower than what is was before even with a single strand of #15.

[s4w2099]

let me correct that. I had a connection problem. Without boost I was getting 1.5A with boost I had about the same maybe  a couple of jumps to 2.5A while boosting. All was taken at about 8Mph.

The only thing I noticed is that while boosting I had a more steady flow of current for longer time.

The 'problem' still exists when I short the mill the blades wont stop as fast as before.