Basic 3 - Phase Stator question

[CmeBREW]

Hello guys.

I finally (!!!) got my first 3-phase stator done and it is in the Vawt windmill, but I am having problem (I think) with hooking up the bridge rectifiers.

I suspect the bridge rectifiers polarity 'markings' are incorrect. I got them from the SurplusCenter catalog. In their picture on the internet their picture is opposite from the ones they sent me. It is also missing most of the markings. Only a positive (+) shows on one corner. So I keep trying it different ways but the DC voltage don't seem high enough after the 2 rectifiers. I hooked them up like Danb's 3-phase hook-up page showed.

So my question is, If the voltage is 8 volts AC between any two wires from the 3-phases (the 3 wires), then what should the total DC voltage be after the rectifiers?

It does around 8 DC volts after rectifiers, at about 60 rpm. I can't find the answer. I thought it would be higher after the rectifiers. The AC voltage is the same for each of the 3 phases.  I was hoping for 12 volts (cut-in) around 60-70 rpm for my New Vawt. It reaches 12 DC volts at about 120rpm.

I just got the thing up a couple hours ago, and there was (of course) ZERO wind. So I didn't have much time to try all different combinations. I had to turn it by hand.

EACH of the 3 phases shows the same 8 AC volts at 60 rpm.

There is going to only be 5-10mph breezes tomorrow,,but maybe I'll figure it out.

Would appreciate any help.

[harrie]

On the rectifiers, the nagative lug should be diaganel from the positive, the other two would be the ac conections from the stator. if you are using two rectifiers, than you would use both ac lugs on one of them, and only one on the other. and yes, your dc volts should be more than measureing two of the ac leads. Of course, you need to run the positive and negative from both rectifiers in parallel to the batterys.

[Devo]

CmeBrew

All of the bridge diodes I have bought so far have one corner shaved off. That corner is the positive terminal opposite to that is the negative(180 %). the other 2 terminals which would be 90 %from positive either way would be the AC inputs..  Does that make sense??

Devo

[Flux]

Perhaps the problem is not the rectifiers.

I see 14 coils in your picture, if it is 3 phase I assume you have 18.67 poles, a fairly unlikely situation. Another dream number out of the hat by the looks of it.

Flux

[tecker]

 Did you finish out Star or delta . Also is that awg 16  on the pig tail .

[Flux]

Sorry, not sure what happened, I counted it 3 times and got 14. Then I counted it anticlockwise and got 15. It has decided to stay at 15 now so that is fine for 20 poles.

With 8v ac you should get about 11v dc.

I would be reluctant to trust any rectifiers that are marked wrong, they will be makers rejects and may have other problems. As the others have said the positive has a chamfer, negative is opposite and the ac are the ones between.

If you have a meter with diode check on it you can confirm with that.

As a final check that the rectifier is working ok, short the dc leads and see that it is stiff and smooth to turn. If you can feel it turning in discrete lumps then the rectifier is not working properly. You should also get the same dc volts out with each ac lead removed in turn ( assuming you can turn it at constant speed). If the 3 single phase outputs are not equal then again you have rectifier trouble.

Sorry about the first post, when I saw who posted it I went back and had a re-count.

Flux

[juddley]

Nice looking stator...

Rectifier Diodes are very easy to test with a multimeter.. This WEB site has a great walk through with pics... loads fast...

http://www.allaboutcircuits.com/vol_3/chpt_3/2.html

You will have to remove from the circuit to test.

It always helps me to keep it straight to make a quick sketch as each pair of terminals is tested.. then I mark them on the bridge so I can remember which is which. There are industry standards for each type of package but I have seen many odddball units with strange configurations. As these are surplus, they may be non-standard.

Juddley

[CmeBREW]

Thanks much,,,I will try those things today. They upped the wind forecast to 10-15mph.

The stator is in STAR and I had encased the other 3 points within the polyester since I knew I would not need them for Delta. The 3 wires are 18 ga. wire and the coil(s) wire is 20 ga. wire by 80 turns ea.(I am not that good yet at winding)

The stator is 1/4" thick.(maybe a hair more toward the center)

So by what Flux said, I assume it is 1.4 multiplied by the AC voltage of each (or;one) phase, is the total expected output. I see now. I hope I didn't get a bad rectifier!  I have 6 - 6amp diodes to try like DAnB showed if I have to.

11 volts at 60-70 rpm would be very acceptable considering I had to open the gap more because the steel mag discs are not running perfectly true. One is a 1/16" off up and down, and the other one is another 1/16" off! - Thats an  1/8 of an inch more on the gap than expected.(Total gap about 3/8")

The mags are 1" dia. by 1/4" thick, N42.

The mill is VERY hard to turn when all 3 wires are shorted. What a magnetic brake!

Thanks for the help. Now I know something must be wrongly hooked.

[CmeBREW]

I forgot this. Heres a picture of it now. Today I might get to see what WATTS this thing will do (if any!) in a 15mph wind!!

[tecker]

You can double the voltage with some current limiting of coarse This should get you charging in low winds . Pick one phase lead and use it for common sort of a center tap adding two doublers one a to c and one a two b.I like to pulse with this but current charge is good or a combination is also good.

[tecker]

Here's another circuit with the coman phase lead as ground

[DamonHD]

You can see a slightly more generic voltage multiplier circuit on my page:

http://www.earth.org.uk/wind-power-pilot-autumn-2007.html

In fact, the top one uses an arbitrary phase as 'neutral' and I'm using the circuit right now.

The next circuit takes more account of the three-phase nature of the beast, but I haven't tried it yet.

For decent charging currents you're going to need to try bigger caps.

Rgds

Damon

[tecker]

The beauty of this circuit is it reestablishes a voltage as the sum of the peak to peak ac voltage plus the ripple of which there's a lot rectifiying with these circuits .The battry eats the ripple up and the caps  can stay somewhat static ,  and easy to switch around . No waste I think the other circuit I posted is a practical and expanable circuit that you can take taps off of  various potientials   to try  match the rpm with the state of charge (el  cheapo) the feed back circuits can be current monitoring or rpm or battery voltage .

[DamonHD]

Right, but if the caps are too small on any of these circuits then you won't transfer much charge (ie current) on each cycle.  If you only want the tiniest of trickle charges then that may be OK.  Else some experimentation may be needed.

Rgds

Damon

[CmeBREW]

Well... Its not looking too good at this point. The alternator I made is not matched well enough to the EXTREMELY LOW rpm of this VAWT wind rotor.

I also realize that my RPM estimates were off. I put a big piece of duct tape on one of the blades and using my stop watch in hand, I can can see now it goes slower rpm than I had previously though. In the VIDEO I had made on YOutube, I now believe it was only going about 100rpm, NOT anywhere near 200rpm!

The RPM range of the alternator is simply way too high for this Vawt rotor.

So this alternator would certainly make a nice low-wind HAWT mill, since it would easily go up past 300rpm. The 12volt 'cut-in' IS about 70rpm.  However, the VAWT rotor rarely goes above 100 rpm.(on a so-called, 10-15mph wind day)

It goes about 100rpm at a 12-15mph wind.  Therefore, it only did 5 stinkin watts or so, at 100rpm.  I could spin it faster with my hand (around 150rpm or so) and it went up close to 20 watts. I expect it will at least make 20 watts in a bigger wind--but the rpm is still very limited and slow.

I did expect more. My very first 3-phase stator WAS a real pain it the A$#^#beep to make. It is NOT one of my favorite things.

I may make a smaller diameter vawt rotor (18" diam by 5 ft. high) to get the speed up.(even though the over-all power will be cut in half)

Or, I can try this 'voltage doubler' circuit that Tecker and Damon mentioned. However, I see a transformer in there , and this is 3-phase, not one. It doesn't make much sense to me.   The Vawt rotor has been turning 60-100rpm for most of the day and with some good torque. But as of yet, I cannot tap into that low rpm range!!!!  Forget gearing--  I am quite certain it looses about HALF the power potential. Thats why I attempted direct alternator drive.

-I will keep trying. Any more suggestions or circuits are most welcome.  -Thanks.

[DamonHD]

Hi,

1. All the circuits shown are cap & diode only: the coils are the coils in your gen.
   
2. I wish I could lend you my 48V PM gen that I'm not going to be able to use for the next few days at least: I'm hoping it will cut in at 12V at ~120rpm or less.
   
   

Rgds

Damon

[DamonHD]

Note also that my top circuit is a multiplier rather than just a doubler: nominally 4x, though more realistically 3x after diode losses from a ~5V gen output.

It does work, but you will need bigger caps to deliver >1W.  I can try to do the sums again if you'd like, but just try it with some cheap caps and diodes and see if you get the multiplication effect at all.  It does work for me on a tiny turbine.

Rgds

Damon

[Gary D]

A quick thought would be to double up(stack) on the magnets. You may get closer to what you want... Just a thought...

[wooferhound]

since it's 3 phase you could jerry rig it to get the voltage up

[vawtman]

Hi Brew

 Your runnin quarter inch thick mags now Right?Whats the airgap between them?mag to mag.I like Garys idea if it can be done with the setup you have.

 Hang in there.

[CmeBREW]

Thanks guys.

Well I do have a few things to try. Probably making the small diameter rotor is my best bet right now. Second is to make another stator with even smaller ga. (24ga) wire. Now, I see that I would rather have 'cut-in' at 30rpm or even 20rpm if possible.

Stacking 40 more magnets just isn't feasible I'm afraid. There is almost 1/16" epoxy over the mags now. I was afraid this could happen because I (in the beginning) had purchased too small of magnets! I am ONLY going to buy 1/2" thick magnets from now on, to compensate for my poorly wrapped coils AND my crooked steel magnet discs. If those 40 magnets on my mag rotors had been 1/2" thick, everything would have worked WAY better I think.

Concerning those basic Voltage doubler circuits, I DO have 3 big AC (big MFd) 'runnning' capacitors and several 6amp diodes, so I may try to see what happens making one of those circuits.  I'm not so sure about the series "Jerry rigged" circuit WOOF showed. The 3 are out of phase, so I'm not sure if that would work. I quess that would take BIG capacitors also. Unfortunetly, I buried the other 3 wires in plastic.

Making the smaller Diametor rotor will not take long at all. First, i will mount the Prototype small rotor on the alternator and see what happens. The hub turns real easy since I cut out the rubber seal on the bottom.

If I get any better results, I will post them here.

Feel free to comment more if you think of anything at all.

[HomegrownPower]

CmeBREW

Great looking job your doing . You will figure it out and make it work I'm sure . ( another newbe here ) hoping to have one flying in a few weeks myself  . I have a few good starts on one waiting on my magnet wire now.

I have # 20 also and some #13 comming . Not sure but I was hoping to do better also ( more volts )   so I sure hope you figure it out . Keep us posted I'll get my results and let you know what I get with 3 phase with number 20 wire

Lonnie

[tecker]

I can sympathize with the down side of vawts you 'll have to make work with one alternate plan so you can get a good idea what it will do  vawts are really toped out at 100 rpm in normal winds . When a northern blows through you can see it run

for a few hours . Wire it up in different ways and carry on.  Scale it up with an H frame .  Stack two more on top and go 2 to one  .  

[tecker]

Drag vawts are topped out at least .

[electrondady1]

cmebrew,

.

congratulations on getting your geni wired up .

i think you have done great for your first one.

i have a collection of 8 volt stators gathering dust around here .lol

wonder if it might be practical to go with six volt batteries?

that way you could let this one live and move on to the next one.

i am curious , if you short the dc leads does the mill come to a  stop?

just comparing the torque your mill produces with the load your alt puts on it.

[CmeBREW]

Thanks Electrondady,

       Yes, If I had a 6 volt battery I am certain it would do exactly what I was wanting. But I do not. The only way to make it work well for 12volt I think, is to have bigger and/or thicker magnets and extremely STRONG magnetic flux with a thin stator to raise the AMPS quickly with the slow rpm. When I short the 3 wires, It is VERY hard to turn by hand. However, the wind rotor STILL manages to turn it slowly even in breezes from the very strong Torque and it should turn fairly fast in bigger winds. I havent had a real decent wind yet above 15mph.

I think this Vawt should still make 40-50 watts in a 30mph wind though. I know 5 watts is laughable right now and I hope the 'flaming' Hawt fellows drank too much at the Hawt party last night. (ha)  -Nevertheless, I WILL figure it out soon. I'm not giving up. I can see and feel the Torque there, I just need to HARVEST that slower rpm TORQUE! (without gearing)  So, yes, this time I failed to bring in the 'Harvest'.

By the way, my 4 foot hawt, did almost nothing (power wise)yesterday on a 10-15mph day. Sure, it went up to 25watts for a several seconds during the best gusts, but it did not last long at all, or accumulate much power. I am still certain this Vawt would do better since it turned from 30-100rpm all day long. (about 8 hours)  If I could just get 1-20 watts out of it it would be very useful since it would be so consistent and accumulate small amounts of power over 8 to 10 hours.

So I will keep on trying to do so.    -Thanks  

[Gary D]

 Hang in there! If you pop over to otherpower.com on the top of this page, and click on the hydro link, you'll see Scotty's hydro project. Dan B. built the stator with a cut in of 38(?) rpm... Thicker wire and larger magnets may well get you there. I think you are very close. Your machine looks great, it just needs a bit of "tweaking" .... Thoughts from the cheap seats, rooting for ya here...

[Flux]

For the power you are aiming for there is no need for bigger magnets, you can lower the cut in speed by using more turns of thinner wire.

If you are prepared to play with simple electronics then you can boost the output voltage of that stator by using a mixed bridge of 3 diodes and 3 mosfets, just drive all fet gates together at about 10kHz, there will be enough inductance in the windings to do it without extra inductors.

The basic power circuit is somewhere in my files. A 555 oscillator followed by a mosfet driver would do to generate the pulses, just set the pwm manually to get the boost you need. I realise that to most people any form of electronics is out, just depends what you are used to playing with. I wouldn't bother with the multipliers and doublers but they may just be possible at such low power levels, I have never found them satisfactory for more than a few hundred mA.

[CmeBREW]

Thanks Flux.  I'm trying to stay away from electonics for now. I just don't have time to study it right now--but I will over the winter.  However,I think I found an easier way.

To everyone,

Thanks for your vote of confidence!

I have some good news. I just put Vertigo JR. rotor on that alternator , and as I suspected, it is doing WAY better now. But there are only tiny breezes right now.

However, It is actually charging 1-5 watts in very tiny breezes! (under 10 I believe)







As I had said before, the big rotor was MISMATCHED for that alternator.

This small 18 inch diameter rotor goes much faster rpm. Probably twice as fast.

The separation of the blades could also have something to do with it.

I now believe its easier to make the difficult alternator FIRST (as low rpm as you can), and THEN try to match a rotor to it. I am understanding more now.

Tomorrow is forecast for some GIANT winds. The biggest in a long time. The weather channel for my area says; 25-35mph with possible gusts up to 50mph!  

Its going to be like a moderate hurricane!  So I will get to see what this little baby can do!!

I got a strong feeling is going to be VERY good.

I will put it in my DIARY if everything goes as I believe it will. (easier to find that way)     -Thanks folks.

[jmk]

 Sounds like your going to need to hook up a dump load. I have been following your progress. I find your project interesting. Your stator looks nice. I can't wait to hear what those winds do for you. Never a dull day when you own a wind mill. For the longest time I used to think windy days were aggravating!

[finnsawyer]

I don't see any iron backing behind that stator.  If there is none then adding one will improve performance.  If you are using such then how thick are both the rotor and the stator iron?

I think at some point you VAWT guys are going to have to take a serious look at the design I proposed in my diary.  Of course, you'll have to do it from the start as you can not retrofit it once you've glued everything down.  The design requires a larger rotor and more coils for the same investment in magnets, but should give more power and a lower cut-in RPM.

In order to keep TomW and that other guy happy I'm suppose to state that it's an unproven design.  Why we need to keep TomW happy beats me except that he wields a big eraser.  In any case, the VAWT crowd keeps running into that too high cut-in RPM wall.  So, maybe it's time to try something different.  

[TomW]

See subject.

I won't lead the thread off topic explaining why its cheap to take shots at people like this or why it should not be tolerated.

Apologies to CmeBREW for my diverging...

[ghurd]

I'm not pretending to know much about it.

Would it help keep the blades a bit more solid with a simple piece of bailing wire in a circle through the center blade holes?  Just to keep them from bowing out at 50MPH.

G-