n50's on a Dan's 10'

[milltech1]

Hello all,

     Got my magnets the other day for my new 10' turbine and realized when I looked at the packing slip that I ordered grade n50's, they are 1" x 2" x 1/2". Has anyone here used this magnet on their 10'mill? Over the weekend I mounted the magnets to the discs and poured the epoxy. Today after work I mounted the rotors on a shaft and made up a test coil. I'm wiring for a 24v system. The windpower book calls for 70 turns of #14. I had some left over from the last stator I made for my 8 1/2' turbine. I wound the coil and came up just a little short on the turns, 65 and I was out of wire. I made up a jig to hold the coil in place and spun the rotor's with my cordless drill and put a meter on the leads, even had the wife help out and hold the phototack to take the rpm readings. At 140 rpm I was seeing 3.9volts from this coil. Even though I am short by 5 turns I managed to get more out of it than I need for a cut of 140rpm. Now what I need to ask before I wind all of the coils and pour the mold, would I be better off to use the #14 wire at 70 turns as per plans and open the air gap, or try using #13 wire and possibly have a slightly higher cut-in voltage? To me it's kind of a toss-up on what to do, but I thought I would get some advice from the more experienced people on the board.

Thanks for your time,

Eric

[Flux]

If you keep the 70 turn winding you can open the gap to get the same result. You have paid for more expensive magnets and gained nothing. If you are in a low wind area it will be fine but it seems a waste of money.

I think Dan's blades are slower than mine but from my experience 140rpm cut in is very low and could be raised to advantage on sites that have a reasonable average wind speed. Whatever you do I don't advise dropping below 140rpm cut in.

This means that you can use less turns and I would not exceed 65 and would probably drop lower. You then have the option of using #14 wire and getting the coils in easily, save a little bit of resistance but not really have significantly more reserve in maximum output, or you can use thicker wire and wind it full and see more benefit from your magnets.

With the lower grade magnets that 10ft machine is great for low wind areas but you really need to be careful to furl it early enough. With stronger magnets and a thicker wire you would have more in reserve and less stator heating. I wouldn't suggest that you push the furling to increase maximum output significantly.

If you keep the same cut in speed with the thicker wire you will hit stall earlier and if you want to keep the output up in higher winds you will either have to increase the air gap ( which would have been avoided with less turns) or you can add a little resistance in the line. If the line is very short then it will need a resistor bit if you have a long line you can use slightly thinner cable and save some cost but the snag is that you really need to run it temporarily on a short line to find out what resistance you should be aiming for.

In the end it depends on your wind area and your load conditions. If you need every available amp on many low wind days then your magnets will not really gain you anything and you may be as well keeping the original winding and opening the gap.

If as here the low wind days give virtually nothing and only blow for a few hours a day it is very detrimental to the total energy capture to push the cut in speed down too low, gaining an amp for perhaps an average of 3 hours a day is a poor trade off for halving the output in a 10 mph wind. It's your choice but it would be interesting to see other peoples views.

Flux

[milltech1]

Thanks for the reply Flux, It is interesting to hear others veiws on something like this. This is only my 3rd genny so I wasn't sure what would be the best way to go, I'm still in the learning process. It's good to have all the folks hear for some direction and advice.

Thanks,

Eric