Phoynex burning

[wpowokal]

Well the Phoynex has lived up to it's name, we are nearing the end of our winter and as usual strong winds. I looked several times during the night but 60 amps were the most I seen from the duel rotor.

That next day despite howling gailes it's output was down and diving, bugger. A slight noise could be heard at low revs, it was impossible to stop it and it howled around unloaded until the next day.

I had gone out and was looking up the tower to see how much deflection was in the tower with such strong winds. Murphy's law interviened and two magnets flew off, one landing some 50m away and the other a little less. When I retrieved the fatherest one it was hot.

The Phoynex story is in the following two links.

http://www.fieldlines.com/story/2005/11/21/123045/41

http://www.fieldlines.com/story/2005/11/13/14104/483

So two days later Grant (Trivio) and Dominic (Domwild) came and we lowered it to inspect the damage.  Now I'm resonably convinced that it just overloaded and burnt out, it did not furl until 15m/s, I will be cutting some off the tail before it goes up again. Maximum wind speed recorded was 21 m/s.

So what we found...

One magnetic rotor was magnet less, it had got so hot the magnets lost their strenght and flew off.

Stator completly burnt..

So its a rebuild, coils are wound and as time permits we will mold a new stator and magnetic disc. Fortunatly we have spare magnets from when it was a tripple rotor.

Suprisingly the front magnetic rotor is as new. This is a five phase Hugh design and one bridge rectifier was kaput, one wire off and smelly (magic smoke all gone), quite when that happened in the failure sequence I don't know.

The nuts holding the stator were loose but it did not show signes of severly rubbing. These were probally the only ones that were not generously locktighted.

allan down under

[wpowokal]

Oh yes the slight noise at low rpm's was the fiberglass disk in pic two ratteling around.

Supprisingly I observed no sugnificant out of ballance, just as well or it would not have survived 24 hours of free wheeling.

allan

[willib]

Yep thats burnt

[Countryboy]

Irfanview is cheap and easy.  You're already making the pics 640 X 480.  Why not lower the KB to under 100?

[wpowokal]

Apologies here are smaller pics, I use photoshop but am far from perfect.

[Flux]

How many coils are burnt ?

This looks to have been caused by rectifier failure.

Flux

[wpowokal]

Flux, five coils all in a row are burnt, only one rectifier has failed.

I had them up in the air, so will be ordering some 10 core cable to at least reach the bottom of the tower if not the battery shed.

The rectifiers are only 400v not the 600v Hugh recomends.

allan down under

[Flying Z]

In Photoshop to resize pic for the web open pic, click "Image", click "Image Size"

under "Document Size" enter the max width you want (or height if that is more important), and then in the "resolution" box enter "72" as that is all most monitors can display so there is no sense in a higher resolution unless you are going to print the picture. When you save do a "save as" so you can keep your original for othe uses. I find that a jpeg compression of about 5-6 if fine for web stuff.

[commanda]

So Murphy strikes again. Anything that can (fail), will (fail).

Amanda

[RogerAS]

Actually the best way to save web images is to use "Save for Web" option after sizing as per above. An option window will appear with a preview of the immage. One can then select a files size (KB) limit and Photoshop will then produce a preview based on that criteria. If one just saves as JPEG or GIF Photoshop saves at the best possible quality. This will be a larger file than the pixel count might suggest.

[TomW]

Allan;

Well not sure about your Phoynex but the mythical Phoenix always rises from its ashes. I remember you telling me about this on IRC but thanks for sharing it out for all to see.

I feel failure reports teach as much and possibly more than success reports in many respects. I hate to see nice gear take a powder, tho. You do not seem to be the type to hide from a challenge and I have every confidence you will rassle it to the ground and get it fixed whether it wants it or not ;=)

Always priceless to have nearby help with similar interests. My hat is off to you and your crew for having the ability to make this kind of device and for sharing the processes involved.

I know you depend on your RE system to make a living so I sure hope you get it back up and solid in time for harvest.

Thanks again for sharing this real world information.

Don't make me come down there...

Cheers.

TomW

[Flux]

Strange. If it was true overload all coils would be burnt. Not sure what rectifier sequence was in operation after one bridge failed.

Why not change it to 3 phase and bring 3 leads down.

Flux

[willib]

ya might want to check that the magnets did not overheat , before putting bad ones back in a new alt.

was just reading about somone who put neos in boiling water to see the effects on 80degree neos , below are the results  , but he is in the process of remagnetizing them , thats as far as i got so far.

http://www.rcgroups.com/forums/showthread.php?t=307133 page two , post number 20 has the data.

he is using a home made gauss meter , hence the voltage readings

i think i'm gonna try to make one , he uses a 4pin ic chip from a old cd rom drive motor.

this is the test :

" " "

Temperature testing

For this test, immersion in boiling water seemed an easy thing to try. It's a pretty constant temperature close to 100 deg C (I'm only a couple hundred feet above sea level) and its self agitating so you get a fairly uniform temperature distribution.

N45

125. mV Before thermal testing
     
98. mV After removing pan with boiling water from stove and dropping magnet in for 5 minutes.
    
98. mV After repeat of above.
    
89. mV After leaving magnet in pan of gently boiling water for 5 minutes.
    
19. mV After repeat of above, but accidentally letting the pan boil dry for a minute or two. Don't know how hot it got, but the Teflon on the pan seemed fine.
    
    

N50

157. mV Before thermal testing
     
92. mV After leaving magnet in pan of gently boiling water for 5 minutes.
    
91. mV After repeat of above.
    
    

So what happened?

The bit of drop testing didn't phase them, but 100 deg C temperatures definitely reduced their strength. Since they are only rated to 80 deg C, that isn't too surprising, but I was surprised to see how much magnetism was left. I also thought it was interesting that both magnets came down to a similar level in boiling water, though the N50 started much higher

" " "

thanks jimovonz for the link ive spent hours reading some pretty interesting stuff

[willib]

Thank you scoop

here is the data again , in readable form

N45

 125 mV Before thermal testing

 098 mV After removing pan with boiling water from stove and dropping magnet in for 5 minutes.

 098 mV After repeat of above.

 089 mV After leaving magnet in pan of gently boiling water for 5 minutes.

 019 mV After repeat of above, but accidentally letting the pan boil dry for a minute or two. Don't know how hot it got, but the Teflon on the pan seemed fine.

N50

 157 mV Before thermal testing

 092 mV After leaving magnet in pan of gently boiling water for 5 minutes.

 091 mV After repeat of above.

[wpowokal]

Flux I'm tending to lean that way, a 10 core cable of suficient gauge will be somewhat bulky. I have to confess I'm still a litle confused at the 10 wires, but then some days are good for thinking and then some are good for sitting under the tree sticking your finger in the honey pot, it's sweet both ways.

We do have heavier winding wire somewhere in the play pen, current coils are 0.9mm x 2, 135 turns, basically to Hughs specs.

Allan down under

[Flux]

It depends where on the demagnetising curve they are what temperature causes a loss.

Obviously these seem to be magnets on their own and will be fairly well down the demag curve, depending on the shape to a large extent.

If they are far enough down the curve, they go into recoil at temperatures above 60 deg C.

If working in a closed magnetic circuit such as a dual rotor the temperature for loss will be higher and likely over 100C.

With keepers on ( negligible air gap) the temperature will be even higher.

I suspect the higher grades will be further down the curve and will suffer more.

High temperature grades are significantly better.

The magnets on the front rotor will be ok, only the other rotor that suffered frictional heating will be affected.

Flux

[wpowokal]

I believe I have finally worked out the failure cause, I suspect the rectifier failed some time ago as I noticed a drop in performance.

This possibly caused some stator vibration, anyway the retaining nuts for the stator came loose on the back side allowing the stator to contact the magnetic rotor.

We either could not fit lock nuts or did not, but also we did not use Locktite. This is the third rebuild for this unit so since things come in three's it should go up and fly forever this time.

allan down under