My little Wind Genny

[Devo]

This is the start of a test genny using 8 neo's per rotor 1"x2"x1/2". It is

still a work in progress I have yet to carve bigger blades ,get bridge rectifiers

& buy a star delta switch But I thought I would start a Diary & go from there.

Thanks to Flux ,Ed & Commanda for the help with math , formulas & The 3 phase wiring.

I will post some specs if the wind ever blows again :-) So far it cuts in at about 150 RPM.

 

[Flux]

Nice looking job looking forward to results.

My immediate thought is that 150 rpm is very slow for a small machine, would be interesting to see how it performs at 24 and 36v, I think extra speed will help.

Flux

[Devo]

I did try 24 volt yesterday & the cut in was much higher nearer 300 I think - I couldn't count it as I was behind the prop when there was a gust & it made .6 amps & started to stall. I can't spin fast enough by hand to verify the cut in

The 5 foot prop seems to small either way , I have a seven foot 5 one as per hugh's internet plans but it is being used on a pm dc motor right now.

So far I see my options as a bigger prop then a star delta switch or 24 volt cut in or straight delta

I am still unsure of a prop size - would 10 feet be enough? Every blade design program I can find has the root drop &  Chord alot more than I thought unless the tsr is up around 8 to 10.

Do I use the high tsr or just do the outside stations as they say at a tsr of 5 or6  

& leave the rest at the max the wood will allow or start laminating to get 3 inch plus thickness?

Thanks

Devo    

[windstuffnow]

  Nice turbine Devo!  What is the resistance of the windings? I'm not sure I would go that large with the prop... the larger you go the less rpm you'll get which will raise the windspeed it will operate in effectively.  You can calculate the output as long as you know the rpm, cut in speed and resistance. If you don't have a way to get the rpm pick up a Tach Jr from Rob its not only a nice tach but a fun project as well...

[Devo]

I have this stator wound in star with 3 leads coming out. If I check the ohms across 2 of those leads will that work? I never checked them one at a time , I guess I should have.

It has 124 wraps of #15 gauge magnet wire per coil 2 coils per phase

Devo

[Flux]

I tend to agree with Ed about the prop size. For normal use I would have thought that your alternator would suit a 6ft prop but I seem to remember that you are trying to make something of very low winds. At present with your low test tower I suspect you have very little wind.

For 150rpm cut in on a 5 ft prop you would need a tsr of about 4 and it looks from your picture that your prop is nearer tsr 7, although I don't know the angles. I think that even on 24v you are well stalled.

The limitation on the size of prop depends on your shaft and bearings, on the general construction, size of tail and finally your ability to hold it down if you do get any high winds.

An 8ft prop tsr 7 would be about right for the 150 rpm cut in and is about as big as I would want on that alternator (if the bearings will stand it). You will almost certainly not be able to stop it by shorting the output in higher winds so bear that in mind if you try it without furling.

Regarding your point about low tsr props and the wide and thick blades, if you make the dimensions correct for the outer 2/3 you can just run out to your board size at the centre part. To make a 5ft prop with tsr4 and use reasonable size boards you would be better with 5 blades.  Tsr 5 on a 6 ft prop would be reasonable for 3 blades.

Flux

[Devo]

I finally put a 7 foot prop tsr around 5 on my Genny. It has been hot & still here but the other day a few small gusts came through at dusk & I had 15 amps at 13.8 volts.

I always like it when the prop is oversized , I feel it maximizes the genny but maybe I am thinking wrong here.

I am going to wind another thinner stator to do tests between them , I think the voltage & cut in will be close to the same because of the increase in flux but I will have less resistance is this thinking correct?

I now have 6 coils 120 turns a piece , 3/4 inch thick stator, I am going to go to 1/2 inch stator propably 70 to 75 turns

I have it up about 20 feet for now for testing.

On another note what is best a chain or belt drive ? I currently have a 90 v dc PM motor running using a belt drive to get a low cut in it seems to work ok except at about 5 to 7 amps the genny stops even if the wind increases -belt slip maybe?

As I look out the genny is just starting to spin slow today - woohoo maybe they'll be wind today , I feel like a kid at christmas except instead of presents I am hoping for wind -lol Very addictive hobby.....

Thanks Devo