What's wrong? F&P alt

[kenl]

 Maybe I should be posting this in the newb section since my experience with turbines has been carve some blades, find a dc pm motor and throw it up in the air (guess I should have stuck with that).

 I purchased a F&P motor from Randy a while back and finally got around to rewiring it and putting it together. I went for 3sets of 4coils per phase thinking this would be a good ratio for the wind I get here. I'm trying to charge a 24v bank with it. Here's a pic of the turbine.


From the picture you can see (I hope there's a picture) that I used some pre-manufactured blades I've had laying around for 3-4 years. They don't seem to have a real good profile to them compared to the ones I've carved in the past. I've yet to see them spin the alt more the 3-4 rev with out a push from me and we have been getting some good wind the last couple of days.

 So a question or two:
 1: are the blades just garbage and should I have carved my own?
2: are 4 coils in series too high a voltage for a 24v system? Each phase is 25 vac before rectifier and battery.
3: is the turbine stalling out due to cut in being too low an rpm for the blades to get up to speed? I'm guessing I'm hitting charging voltage around 60 rpm.
4: should I just stick with what I know? Solar.

Thanks, kenny

seemed like a good idea at the time

[Flux]

The picture doesn't show it very well but I strongly suspect the blades are on backwards.

Added to this I really doubt that you have much useful wind at that height, you only look to be a few ft above ground. it is very easy to mistake the turbulent mess at that height for real wind.

The top things and cogging from the F & P is likely to be your trouble.

Flux

[Flux]

Just a few other points. you will not be stalling at that speed from cut in issues but you may possibly have reconnected the windings incorrectly and have a lot of drag that is preventing the blades picking up speed enough to start.

You would probably be able to feel this when hand cranking the alternator but it is not easy to judge how much drag you can tolerate.

Flux

[kenl]

Flux,

 I'll check the blades. Nope profile is down wind and flat side to the wind, just checked. The turbine is on a test stand right now for ease of adjustment, the winds are from the south and there is a steep hill to my south. I've always gotten my best winds from this direction because a valley below me funnels the winds this way. I do get turbulence though. The pm motors I've used in the past have always preformed well on days like today.  I'm using a 36 pole stator "cog-less" stator but you may have something there.

 I did and open circuit metering after the rectifier and was reading between 50-60 vdc at about 80 rpm. Could the cutin at low rpm's be a issue you think? I believe it was you 4-5 years ago trying to explain stalling to me but I'm not sure I ever really understood it. The turbine will keep spinning with no load and a push from me in these winds, but will not self start or continue spinning if a load is applied. Maybe I'll try a 48 vdc bank and see if it will keep spinning. That should get the rpms up before it sees a load from the batteries.

Thanks for the input, kenny

seemed like a good idea at the time

[tanner0441]

Hi

I go with Flux looking at the blades, and if you say they are for down wind what is the tail doing? Down wind turbines don't normally have a tail....

Brian.

[kenl]

Brian,

 The profile side is down wind, the turbine is not a downwind turbine. I'll snap some pics and post, sounds like this may be a good poll question. "which way would you face these blades"  Maybe I'm looking at these the wrong way.

 kenny

seemed like a good idea at the time

[Simen]

It's hard to guess from the picture, but it seems that those blades are around 1-1.3m long (2-2.6m diameter), and in my understanding; 60rpm would be too low for cutin speed for those blades...

[ghurd]

What is the blade diameter?

Is it wired Star / Wye?
Might try IRP / Jerry Rig to get the cut in RPM higher.

2)  The PMA voltage is clamped to the battery voltage.
If the PMA side of the rectifier is always about 1.4V higher than the battery, and the blades don't get going faster in more wind, sounds like stall to me.

3)  60RPM cut in is not right.  "50-60 vdc at about 80 rpm" means 24V cut in around 40 RPM.
That cut in of 40RPM sounds like it could cause a stall issue to me.

G-

[kenl]

Here's some pictures of the blades.





Simen,  the blades are 4' for a 8' sweep. Probably too large for my tower since it was designed for a 6' swept rotor. And that is kinda pushing it.

kenny

seemed like a good idea at the time

[Simen]

8 feet diameter... i'd guess 130-140rpm  would be close to cutin... With those extra wanes near the center of the hub, you'd get an easier startup, wich is good for an f&p gen...

Now, i'm not the expert here; haven't even got my own 7' up in the air (which have an confirmed cutin @ 160rpm), so i'm sure others will have their say...

[kenl]

ghurd,

 The stator is wired star since I'm going for low wind performance. I'm not looking for loads of power out of this just floating a bank of batteries that I use on occasion. I tend to agree with the stall theory maybe a 48v bank would be a better match or re wiring the stator, less poles in series to drop the dc output and let the poor thing get to a higher rpm. This is my 1st real alternator build and it looks like I'll be learning a lot through my failures. I do have some reservations about the blade though. They don't seem to have enough pitch to get the thing spinning, maybe its just me.

kenny

seemed like a good idea at the time

[Flux]

Now that I can see the blades I agree they are the right way round.

The cut in is way too slow, you will hit stall during start up. Not sure of your prop diameter but I think 24dc at something near 200rpm is what you will be looking for, you have something like 5 times too many turns.

I am not familiar with those F & P things, they don't exist here but I believe they will need a lot of parallel circuits to get down to 24v. Have a look on the Australian web site ( back shed or something, I have lost the link since the computer crashed), they are the experts on the F & P, you should find lots of help there.

You have more or less confirmed the stall issue when you say it will run on open circuit but fails to pick up speed when connected to the battery. If you can connect it for a better voltage match you should make something of it, but start up may be poor, Not sure if you can mount the blades to give a bit more pitch to help starting.

Just found the link    http://www.thebackshed.com/windmill/home.asp

See what you can find there.

Flux

[Flux]

I see that you say the blades are 8ft diameter, in view of the fact that the  F & P is not going to be much of a low wind machine I would suspect that cut in at 180 rpm may be near right. If you go slower i don't think you will gain, the iron loss and drag from the core will defeat you in any winds much below 10mph.

Flux

[kenl]

This is what I'm use to using for blade. Disregard the cracks this is one of the 2 I found after the hub let loose and the blades slapped the tower. Notice the steep angle at the root for getting them started. Thanks Ed these were cut from the instructions from your web site and work well.




Flux, There rewire was done per instructions for a "good all rounder" off the back sheds web site. I think they descibed it as a good low wind 12volt or high wind 48 volt, couldn't find much info on what size blades to match it with or wind speed required to keep it spinning though. But it looks like a re wire will be the next step right after I finish the 48 vdc bank tests.

 Thanks to everyone for your input, kenny

[kenl]

Here's an update on the F&P:

 In order to correct the stalling issue I was experiencing I figured that a 48 vdc system was better suited for this alt. I am still haveing some stalling issues but not as sever as before. I did carve some wood blades to replace the factory made ones but that only improved starting a little. I think the F&P just needs more push to get going then what is typically built here. The stator is still wired 4 coils in series, though 2 or 3 is probable a better arrangement (even at 48vdc. I did build a new tower over the last couple of weeks to get up in the air more and have something more rigid to put the turbine on, so far it is holding up well but could stand to be 20' taller.
 Things I will try from here are wiring a new stator with less coils in series and maybe changing the blades from 7' dia to maybe 8' dia sweep. hopefully the increase in swept area will help low wind start up. Any ideas will be welcome and thanks to all who have given input.
 Here are some pics. The one with the meters is from this morning. The multi meter is vac across 2 phases, the analog amps into the 48 volt pack and on the right is battery voltage using an old southwest wind controller. I use the controller for dump only since the turbine does not seem to run smooth if the ac is run through it. Rectification is through a 80 amp 3 phase rectifier.

[kenl]

 Had a chance to try some experimenting today to find the sweet spot for this alt as wired. Wired 8 12v 100ah batteries in series and let it run in 10-12 mph wind with gusts to 20 so said the weather channel. Seems that this is where the stator wired 4 coils in series is happy. Turbine was pretty much continually spinning putting out around 110-115 vdc at 2-4 amps depending on the gusting of the wind. My intent for this turbine was to charge a 24 vdc battery bank but I don't think after messing around today that this is a realistic goal. 48vdc seems to be the only other alternative with the stator wired 2 coils in series. This being a 36 pole stator would give me 3 phases of 6sets of 2 coils per phase. Seems like it should produce pretty good output in this configuration.
 Can anyone suggest a suitable swept area for this? Would increasing my blade length help? I could use better low wind performance. I do feel that I'm limited on how large of blades I can go with due to my home built tower. 8' would be close to as big as I would feel comfortable putting on it.
 Well that's it for now, more wind tomorrow so I'll be able to do some more testing 

kenny

seemed like a good idea at the time

[Flux]

I am glad you sorted the stall issue. For low wind performance there is no substitute for blade diameter especially with iron cored alternators where you have an inherent loss before you get any charging.

If you think your tower will stand 8ft then go for it but make sure your furling will still work as larger blades need more offset.

Flux