Serial or Delta for small windmill

[GBillerty]

Hello!

I want to built 1 small windmill for remote cabine " hunting camp" I'm looking for 200-300 Watt turbines with small 3 blades prop around 4-5' diameter. I would have to charge one or two 12V batteries, not more.

I was thinking of 8' diameter dual rotor wired in delta

12. Neos mags  1" X 1" X 1/2 "
    
9. Coils 50 turns of 15 AWG
   
   

OR

8. ' diameter dual rotor wired in serial
   
12. Neos mags  1" X 1" X 1/2 "
    
12. Coils 50 turns of 15 AWG
    
    

I want to get the lowest cut in speed possible

What do you think about that?

thanks for you help and ideas!

 

[DanB]

By 'serial' it sounds like your planning 12 coils all in series - that would make for a single phase machine.  

I would do the 3 phase machine with the 9 coils and hook that in star...

You might test one coil first, and get some idea of what cutin speed you'll actually wind up with.

You really dont want the 'lowest cut in speed possible'...  you need the cutin speed to be appropriate for your blades.  For a machine of that size, 250 - 300 rpm would probably be nice.  Too low, and the blades will stall and you'll have very poor output from it.  Lots of folks have the idea that a lower cutin speed means more power in low winds.  That's not always the case...

[johnlm]

G,

Which size prop do you plan to use?  In the first portion you say 4 to 5 ft diameter then in the lower sections you say 8 ft rotor.

As Dan suggested, you have to careful trying to go too low on cutin. If you want low cutin wind speed then you just about have to use a much larger prop than is really needed once the wind gets much over 10 to 12 mph.  Its a trade off, and the selection is influenced by the local wind speeds.  If the average is in the 7 to 9 mph range then going for a large prop (for a given alternator) and low cutin is better.  If the average is from 10 to 12 then a mid size is a better choice.  If the average is above 12 mph then a smaller prop with a higher cutin speed is better.  Just a ballparking suggestion, and my opinion.

John

[GBillerty]

I had a 8' 3 blades prop made for a bigger PMA... I was planning to use it but as per your writings, this will be to big for my PMA ( stall problem ).

each blade is 4' long, can I only cut/remove one 1' from each blades or it would be better to carve some brand new blades for a new prop.?

thanks again, you are very helpfull!

[Flux]

If you really want good results in low wind and are prepared to furl very early you can use your 8ft prop if it has a tsr of about 7.

If you are stuck with the #15 wire you should be able to use about 120 turns per coil, 9 coil delta connected. There should be room .

About 70 turns of #14 connected star would be a better winding for best results in low wind.

You could use those magnets on about 11" disc with a stator about 5/8" thick.

Don't use the single phase 12 coil arrangement, you will not hold an 8ft prop down with those magnets.

Flux