16" duel Rotors

[harrie]

I plan on doing a complete post on this turbine, when I get done with all the testing. So far, it seems like its going to be a dandy. I just decided to throw this picture in now, thinking that DanB could view the extra support for the stator. The angle Iron is 3/4" X 3/4". I think it gives the flat stock alot of extra strenght.

And yes, it is another tilt back furl.

Great Fun, Harrie

[Nando]

Harrie:

Excellent work, I congratulate you !. Nice DUAL Rotors

Can you inform, in detail, the capabilities of the generator?

Can you select output generator configuration i.e. STAR or DELTA ?.

Phase winding resistance.

Generator Volts/RPM

Wind mill power curve

Wind mill peak power @ Peak RPM

Wind mill peak RPM

Battery bank voltage.

Wind Regime in your area.

What type of charger controller are you planning to implement ?.

Regards

Nando

[willib]

Damn i could cry that looks so sweet..

you do nice work ..

i have a lot of questions too but i'll wait , just one for now ..

what type of tool is this?

it looks like it really tears into  the wood..

http://www.otherpower.com/images/scimages/1412/100_0093.JPG

[kitno455]

angle grinder with a flap disk. they come in several grits, but they are basically a fiberglass disk with pieces of sandpaper stuck on them, though i also have one with bits of scotchbrite pad for cleaning machined gasket surfaces.

allan

[harrie]

willib, gosh, I dont know how that picture got in there, I have a series of pictures about how my blades were made, and planed on posting later. But anyway, that is a metal cutting flap sander that fits on the angle grinder, and yes it removes wood very fast, and is great on the radius cut out at the root.

[harrie]

Hi Nando, well like I said in my previous post, my abilities in electronics are limited, but because of you guys, I have learned alot.

So far, using my not so good meters,

After rectifing, 12 volt cut in 15 RPM

                 24 vott "    " 50 RPM  In Star.

                 48 volt "    " 100 RPM

      In Delta   12 VDC          50 RPM

                 24  "           95  "

                 48  "           175 "

Phase Resistance, Im unsure of yet, due to my meters. I am trying to find a better meter that will tell me this.

Wind is rated at #2 , most of the time it averages 10 to 15 miles per hour.

I already have a morning star 60 on my 12 volt bank that has worked very well with the 12 foot 12 inch duel rotor that I have been flying for a year now. This one is for my son, who will have a 48 volt bank, and will be mounted on top of a 80 foot fire tower.

Thank you all for coments.          

[Nando]

Harrie:

Are the voltage readings done unloaded generator or what ?.

Taking the first reading : 12 volts @ 15 RPM gives 0.8 volts/RPM and if at 200 RPM the voltage would be 160 Volts.

So read the phase winding resistance ( from common to end) or (from end to end) in STAR configuration -- and I can tell you how much more power you will be able to harvest with a proper charge controller with MPPT.

Also with a MPPT Charge controller you may be able to close the Stator-Rotor gap to a minimum, to produce higher voltages at lower RPMs to attain a higher power output.

Nando

[willib]

thank you both !!

this place is a neverending supply of information, gotta love it..

[harrie]

Nando, yes, unloaded generator.

Tell me if im wrong, but to try and take a resistance reading when the stator is between the two rotors will give false readings. I tryed to take readings when the stator was off, using a degital Ohm meter, and it showed 1.5 ohms per phase, which I thought was kind of high. I plan on takeing it apart again when I get the other meter.

Other information, is the coils have 60 turns 2 in hand #15 mag wire. Magnets are the 2"dia X 1/2". 16 mags per rotor, and 12 coils.

Rotor is 1/2 inch thick,  Total Gap between mags is 11/16th.

It turns very free without load, when hooked to batterys, It becomes extremely hard to turn, but I think the 18 foot prop will crank out enough amps to charge the system.

I think I am still at a point of trial and error, due to not understanding all the calulations.

Thanks harrie

[willib]

Harrie resistance of coils like yours have to be calculated by the length of wire used , a ohm meter isnt gonna cut it..

[Nando]

Sorry, an Ohmmeter will do, it has been doing since the late 1900 !!!! EVEN if in a magnetic field (the magnetic field must not be moving).

Nando

[Nando]

Using the 1.5 ohms, the dynamic ohms are = 1.5 * 1.73 = 2.6 ohms

Using a MPPT charger

At 300 RPM suing your data the generated voltage would be 300 RPM * 0.8 V/rpm = 240 V that 3 phase rectified is = 338 volts ( less ripple) lets say 300 volts

If we assume 10 % losses in the generator = 30 volts

Current= 30 / 2.6 ohms = 11.54 Amps

So the delivered Voltage would be 300-30 = 270 volts

Power out = 270 * 11.54 = 3.1 KW

Power dissipated by gen = 30 * 11.54 = 346.2 Watts

If instead of 10 % we assign 15 % losses to the generator then:

300. -45 = 255 volts
     
45. v / 2.6 ohms = 17.3 Amps
    
    

power out 255 * 17.3 = 4.4 KW

Power dissipated by generator = 45 * 17.3 = 778 watts

SO It is always BEST to close the rotor-stator gap and produce the highest possible voltage to attain the greatest efficiency.

Direct charging ( 1/2 Power Wind Mill) at 300 RPM with 300 volts the power distribution would be 300 - 56 volts = 244 volts to be dissipated by the generator with 2.6 Ohms resistance.

Do you care to calculate the power dissipated by the generator ?.

So the system needs to fly at lower RPM like around 150 RPM.

Nando

[Nando]

I NEED TO NOTE

That these calculations are "estimates" and "wild guesses" until a GOOD Set of DATA and the setting of the wind mill can be adjusted to obtain the best MPPT output.

Regards

Nando

[picmacmillan]

hi guys..those things can be bought at any harbour freight in the states or any princess auto in canada..like was said they can be attached to an angle grinder..what i use on my log homes(and blades) is the same kinda deal, except i use 28 grit sandpaper instead of the flappy disc..does a great job and is way cheaper..you can buy a little rubber or plastic backing plate for your grinder to use any grit sandpaper ...i should note this is how i do all my blades also......i did buy one of those lancelots that dan had, and like he has said before it is the most dangerous tool known to man, but it also takes out alot of material quickly but you wouldnt want to make a mistake or your work is finished. i would recommend either that flappy disc, or 28 grit sandpaper to do a nice job...of course we use that soon to be 100 year old tool to start the blades and that would be the sawzall(just kidding about age)! give er!    pickster

[picmacmillan]

hi harrie...very nice job my friend..i am right behind you doing pretty well the same thing...i am still contemplating myself on which way is the best way to support the stator to reduce the chances of failure once the stator gets hot...

  danb said his stator reached over 400 deg. far. before the wire melted...i am guessing here, but i would think the heat made the stator curl, and i am furthering my guess that it curled from the inner circle of the stator where there is no support..

 in my humble opinion we need to find a way to stabilize the inner most circle of the stator, and anyone with suggestions i would be glad to here them...because the bolt circle for our blades is connected in the inner circle of our stator, then making this one solid piece is not an option...

  i was just pondering changing the place where we connect our blades to the outermost ring, therfore allowing us the option of making the stator more rigid from the inside out..reinforcing it across the center to the other side reducing the stators ability to twist..

great job harrie, nice to see your work...good luck on your project...pickster.....

one more thing...

 has anyone done any testing on what the linear expansion of the copper wire is? and for that matter the fiberglass resin?..our airgap for the most part is very small, if that wire expands(and it does),it may be an important factor in maintaining the proper airgap when heat becomes a factor....pickster

[phil b]

Harrie, you've done excellent work! I use angle iron to help stablize my stators also... usually come from old bed frames from the landfill.

Hi pickster,

IMHO, we need to somehow reduce the amount of heat that the mills generate. Heat is lost watts and ultimately, failure. More magnetic material and less winds of copper? Professional mills claim less than 1 ohm. So that might be a starting point for guess at a lower heating type configuration. Much easier said than done. Over the past year, I've wound many different stators looking for the most power and heat low enough to can live with.

Good luck

Phil

[willib]

that is a good point picmacmillan,

as the copper expands it would push outward against the resin or epoxy thus cracking it.

i think  that leaving the hole in the coils empty , so air can cool them is  a good idea..

maybe we just need a better resin or epoxy to use on the stators..

[ghurd]

I use some epoxy potting compounds for other purposes.  The plastic box will melt or deform before there is a failure in the copper... usually... I think...  Obviously a semiconductor failed to make it get that hot.

Problem is it costs close to $300 a gallon now. Kind of brittle too. No coils in there though.

Maybe if just a slot was cut in certain places it would handle any expansion problems?

G-

[SamoaPower]

Exactly, Phil!

Most people have been addressing the wrong end of the horse. It's my current favorite soapbox topic. If as much thought and effort was put into solving the basic problem as there is in finding bandaids, we'd be further ahead in the game.

The basic problem, of course, is the progressive lousy efficiency of the PM alternator with increasing speed when charging batteries and it's not only a high-end problem. This results in less deliverable power and increasing stator temperatures. The real issue is load matching.

It's my opinion that changing coil detail and phase/rectifier configuration won't be sufficient to solve the problem to the degree needed. Electronics can. Many seem to shun the idea of electronics, citing complexity, low reliability, cost and lack of knowledge and skills. I wonder if they feel the same way about their computer that they probably use daily and is an order of magnitude more complex than that needed for alternator load matching.

Enough ranting for the day. Let's attack the real problem Phil.

[willib]

SamoaPower how would an extreamly low stator resistance do , with what you are suggesting?

thinking  electronics could boost the alt. output voltage of a low voltage, really low resistance , high current stator ?

http://www.fieldlines.com/comments/2006/3/9/41535/22981/10#10

i got a calculated 40A rms from one coil at 200RPM but the voltage is a little on the low side .

granted i was loading it down alot..

at 227 rpm the no load voltage is 1.5 Vpeak

[drdongle]

I would think that expansion slots, like those used in side walks would be a possibly answer. Try a slot between each coil and it neighbor. This might take some rethinking of the stator mounting as slots might significantly weaken the structure of the stator

[BigBreaker]

Supposedly you can make low electrical but high thermal conductivity casting resin by adding aluminum powder to the standard stuff.  Aluminum flexs should be pretty cheap.

[ronksl8]

Why are the stator coils not wound on laminated metal.

[willib]

The easy answer is the cogging effect..

the tougher question is why couldnt a laminated stator be made with very small gaps between coils ,which would produce almost no cogging?

answer is money and time..

it takes no extra money to not install a laminated stator. double negetive much..

the time it would take to produce such a stator would add more cost to the project..

[canadianfred]

You mentioned that your windmill is using a tilt-back furling mechanism.

Can you upload close-up photos of it?

How did you determine the correct strength of spring to use?

[harrie]

I will be posting a complete construction story on it in about a week, My wife took off with the camera so have to wait until she gets back to take additional pictures. The Tilt system is still in the testing stage, The springs are adjustable, and will also depend on tail weight. I will probley have to play with it on a test tower to get it right. In my other stories, you can look at the first one I built which has 12 foot dia blades. even tho it is still working fine after a year, I have made some changes to this one. the 12 foot depends on springs to make it furl, this one has the springs to bring it back down.

[SamoaPower]

willib,

Unfortunately, as Amanda and others have pointed out, the dynamic source impedance of the alternator is complex and variable and more than a simple resistance. Likewise, a battery's input impedance is also complex and variable (dependant on SOC) and more than a simple capacitor. Also, there are other elements such as the transmission line which has resistance, inductance and capacitance. With this complex dynamic model it's hard to see that a static solution (lower coil Rdc) will provide a match over the operational range of interest although it could help.

Fortunately, MPPT, suggested by many, has the potential to simplify the problem. If we can dynamically maximize power transfer, we can come close to a match.

[scoraigwind]

You will be looking for a cut in around 80 rpm for the 18 foot rotor, I am guessing.  But the atlernator seems a bit small for this size of rotor.  Better set the tilt back for easy furling in the beginning I would say.

hard to know which voltage and which star/delta.  If you are already 12 volts, you could try using the 12 volts at delta.  Not my favourite - I prefer star - but matches your battery.  Use a resistor in series to get good speed matching at least at fisrt so it's up and running.  Only problem is the huge cables you would need.

Personally  I'd be tempted to try 48 volts star at 100 rpomm cut in although it would be noisy and unproductive in low winds.  Going for a higher cut in gives you more current delivery into the battery with less heat.

[harrie]

Thanks for the Input Hugh, Yes the prop may be a bit big. My thinking is I can always shorten the blades, but its kinda hard to lenghten them. Ha. This one is for my son, and he will have a 48 volt bank. Why do you think it will be noisy in lower wind speeds???. I build my props with very little pitch on the ends, they are very close to flat. I think it helps keep the noise down??.

Thanks all for your comments

Great Fun Harrie

[ghurd]

My use must be 100% proven electrical non-conductive (often involving FETs in the mix).

Thermal conductivity is a high priority.

Al, Fe, etc, almost always short the circuits.

Plain sand often does work, and we often use it for 'cutting the mix' in larger volume of filler products.

I figure many of the loose iron core based machines have substaintial iron losses and/or eddy currents.  IMHO.

G-