Author Topic: Help with motor conversion  (Read 7524 times)

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bigrockcandymountain

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Help with motor conversion
« on: August 21, 2016, 07:55:53 PM »
Hello everyone,

I'm hoping to do a zubbly conversion on a 5hp motor that I picked up today. 
It is a 200v 3 phase 3 wire 1715rpm motor.  I'm hoping to use the original winding but that may not be the case. 

I took it apart today and the winding pattern seems odd.  The inside coils are concentric but only fill 4 slots so slot 1 2 8 and 9.  Outside are the same and there are coils buried in the middle too.  The winding looks fairly heavy and in good shape but there are only 3 wires coming out.  It has a lot of sleeves on the stator winding that could likely be taken apart and wires added if I knew what I was doing.  I was hoping for a 8 10 12 concentric. Maybe with a little advice I can figure this out.

Would this be wired delta?  Should I just do up the rotor with mags and see what voltage I get. I have a 48v system so cut in needs to be quite high at low rpms. 

Any advice on magnet thickness, machining, wiring, testing or any other advice go ahead and offer it.  I'm very new to this. Looking for close to 500w at 15kph wind or so and about 2000w max.   

Thanks in advance.

Adriaan Kragten

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Re: Help with motor conversion
« Reply #1 on: August 22, 2016, 06:06:48 AM »
From your description it isn't clear to me what kind of stator winding you have. If you make a photo of the winding may be it becomes clear. Om my website: www.kdwindturbines.nl you find free report KD 341 at the menu KD-reports. Figure 1 of this report gives the winding of a 4-pole PM-generator made from a 4-pole asynchronous motor for a stator stamping with 36 slots. This is a so called 2-layers winding. The three coils of one phase in the first layer are normally connected in series to the three coils of that phase in the second layer. It is possible to connect the layers in parallel in stead of in series which halves the voltage and doubles the current. This modification of a 230/400 V winding into a 115/200 V winding is illustrated in figure 2 of KD 341. These figures count for an European motor which is used on a 50 Hz, 230/400 V grid in star. In America the voltages and frequencies may be different but I think that the winding can be modified in the same way.

The voltage generated in the bundle of three coils of the first layer is the same as the voltage generated in the three coils of the second layer, so it is allowed to connect the bundles in parallel. The coil pitch angle of the three coils of one bundle is not the same. The angle of the inner coil is 70 degrees, of the middle coil is 90 degrees and of the outer coil is 110 degrees. The magnetic flux flowing through the middel coil is maximal because an angle of 90 degrees corresponds to the angle in between the magnets of the armature. The voltage generated in the middle coil is therefore highest. The voltage generated in the inner and outer coils is lower (if all coils have the same number of turns per coil). It isn't allowed to connect the three coils of one bundle in parallel because this will give an internal circulating current. So it isn't possible to reduce the voltage by a factor 6 by connecting all coils of one phase in parallel.



 

joestue

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Re: Help with motor conversion
« Reply #2 on: August 23, 2016, 03:56:13 AM »
Do you have a 24 or a 36 slot motor?
are there any empty slots?

Adriaan, i've never heard of a motor that is wired with coils that are wider electrically than they need to be, they are always narrower so to speak. but perhaps its just semantics.

for example, the 24 slot 2 pole generator I wound with coils that spanned 10 slots. i can make a coil that spans 12 slots, which would generate a little bit more electricity at the expense of adding 10% more copper (would have had to make the coils 4 inches longer). so the winding is 10/12, .8666 or 155 degrees wide, out of 180.

But i can't make the coils span 13 slots, i mean i physically could, but electrically it would be just the same as a 11 slot winding, but with much longer wires to reach around the other side of the motor.

In all the motor engineering books i've read the electrical width of the magnet and coils are converted to 180 degrees. so for a two pole motor, the magnets span up to 180 degrees, usually 150 to 170 degrees. in a 6 pole motor, the magnets are still 150 to 170 degrees wide, but physically they are less than 60 degrees.

(the rotor in my generator was only 90 degrees wide, with a varying airgap, i could have converted it to 4 poles by bolting on two more arc shaped segments and reconnecting the two halves of the coil to oppose each other)



btw, when i was trying to decide how to rewind my generator, i looked around on the net for all the photos i could find for large two pole turbo generators.

most of the two pole generators i found were wound with coils that span 17 slots, the generators being 42 teeth. makes for a ratio of 9.42:24. some of them were wound with coils that spanned 24 slots and 60 tooth core, for an even ratio of .8 or 144 degrees, or 9.6:24. so i made mine 10 slots wide.

edit: so i google a bit again, looking for more photos.. found a lot more. its like google found more images for me. found some 72 tooth machines, also an 84 slot machine (might have found an 78 slot, two pole machine just now) http://www.ethosenergygroup.com/_catalogs/masterpage/ethos/img/slides/stators-rotor-rewinding-slide1.jpg and it looks like the core is split in the middle and shifted half a tooth.
« Last Edit: August 23, 2016, 04:05:23 AM by joestue »
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bigrockcandymountain

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Re: Help with motor conversion
« Reply #3 on: August 23, 2016, 09:23:57 AM »
Thanks Adriaan and joestue.  It is a 36 slot stator.  Your right that the coil spans are only 9 slots.  I'm thinking it's 12 coils 4 per phase.  Each coil fills 3 slots as the outside winding fills a whole slot and the inside fills only half the slot and is shared with another coil. I'll try to get pictures for you guys.  I get the feeling it's delta but can't be sure without some digging. 

I'm thinking I'll do the rotor up and see what it makes and get into the stator if it's not useable.

I'm thinking 50mm x 25mm x 10mm mags.  They will overhang the rotor by 10mm on each end as it's only 80mm long.  They are cheaper than 40mm long mags though.  Advice on glueing or drilling and screwing or anything would be great.



 

joestue

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Re: Help with motor conversion
« Reply #4 on: August 23, 2016, 12:48:04 PM »
one way to hold the magnets is to cut slots slightly deeper than the magnet, peen the edge of the metal over.
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hiker

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Re: Help with motor conversion
« Reply #5 on: August 23, 2016, 03:16:40 PM »
Always thought that wasn't advisable ...as in making slots in the metal rotor..distorts the magnetic field..end up with a weaker magnetic field being directed towards the coils..

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joestue

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Re: Help with motor conversion
« Reply #6 on: August 24, 2016, 12:51:45 AM »
Always thought that wasn't advisable ...as in making slots in the metal rotor..distorts the magnetic field..end up with a weaker magnetic field being directed towards the coils..

at the risk of epoxy failing, i would not bother chasing the last five percent.

a 5 hp 4 pole motor, 10m deep magnets will probably reach close enough to the bottom of the aluminum bars, making a new rotor won't be cost effective.

given that its 5 hp and 4 poles, he can probably fit 12 magnets around the circumference, maybe 14 but probably not worth it. the flux lost due to the metal holding the magnet on, will probably be less than the flux lost in the air gap due to the 25mm wide magnets. but smaller magnets means higher cost per cubic inch of magnet.

Might entertain offsetting the rotor magnets by 5 degrees in the middle of the rotor to reduce cogging.
« Last Edit: August 24, 2016, 01:00:03 AM by joestue »
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Adriaan Kragten

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Re: Help with motor conversion
« Reply #7 on: August 24, 2016, 05:09:55 AM »

Adriaan, i've never heard of a motor that is wired with coils that are wider electrically than they need to be, they are always narrower so to speak. but perhaps its just semantics.

For a 4-pole PM-generator, the angle in between the magnets is 90 degrees. So the ideal angle for the two legs of a coil is 90 degrees too. But this can only be realised for a 3-phase winding if the stator stamping has only 12 grooves. If the stator stamping has 36 grooves one coil gets a larger angel and one coil gets a smaller angle. The coil configuration given in figure 1 of KD 341 is the standard configuration of asynchronous 4-pole motors of European manufactureres.

For a 6-pole PM-generator, the angle in between the magnets is 60 degrees. So the ideal angle for the two legs of a coil is 60 degrees too. But this can only be realised for a 3-phase winding if the stator stamping has only 18 grooves. If the stator stamping has 36 grooves, one coil gets an angle of 50 degrees and one coil gets an angle of 70 degrees.

It is possible to give all three coils of a bundle of a 4-pole motor the same angle of 90 degrees and to place the coils like tiles, so one coil in groove 1 and 10, one coil in groove 2 and 11 and one coil in groove 3 and 12. However, mounting of the coils this way is more difficult and the voltage generated in the three coils of one bundle is not in phase. This type of winding is generally not used in motors of European manufacture.
« Last Edit: August 24, 2016, 02:55:52 PM by Adriaan Kragten »

Adriaan Kragten

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Re: Help with motor conversion
« Reply #8 on: August 24, 2016, 05:28:20 AM »
In my free report KD 503, I give detailled information about the design of a 4-pole PM-generator made from an asynchronous motor frame size 100. Fluctuation of the clogging torque is prevented by chosing an angle in between the grooves and the shaft axis such that there is exactly one stator groove overlap. Magnetic short-circuit in between a north and a south pole is largely prevented by chosing a small bridge in between the poles and by using an aluminium bush in between the armature and the shaft. Figure 1 of KD 503 gives detalled information. Measurements for a similar PM-generator are given in free report KD 78.

It is important that the stator stamping is not provided with four outside grooves in which four strips are laid (bent at the ends) to connect all stator laminations. This is often done for stator stampings of Indian manufacture. The four outside grooves give four preference positions per revolution even if the armature grooves have the correct angle.
« Last Edit: August 24, 2016, 05:54:22 AM by Adriaan Kragten »

bigrockcandymountain

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Re: Help with motor conversion
« Reply #9 on: August 24, 2016, 02:01:11 PM »
The stator has 8 grooves with straps and bent ends.  Will this cause the same problems as 4 slots?

What is the best kind of epoxy to use?  I have JB  weld and t88 epoxy.

Has anyone drilled holes and screwed them on?  I found a method for drilling without heating them up but would the holes wreck the magnetic field?

Adriaan Kragten

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Re: Help with motor conversion
« Reply #10 on: August 24, 2016, 02:51:07 PM »
Four magnetic loops are coming out of a 4-pole armature. However, at the position of the magnets, almost no magnetic flux is coming out of the armature. The magnetic flux flowing in the stator stamping is hindered by an outside groove and the stator stamping will be saturated just below the outside groove if you use strong magnets. However, this effect is minimal if an outside groove is just opposite a magnet and this results in a larger magnetic flux through the  stator stamping for this position. A larger magnetic flux results in a preference position. So for four outside grooves you get four preference positions when the four magnets are opposite to the four outside grooves. If you have eight outside grooves, you will get eight preference positions but the peak torque may be smaller than for four grooves. A too high peak in the sticking torque gives a too high starting wind speed.

I have built a 4-pole generator with an Indian stator stamping with four outside grooves and the peak torque was about four times higher than the sticking torque at the positions in between. I have also built 4-pole generators using European stators with no outside grooves and those generators have no peak on the sticking torque if the angle in between the grooves and the shaft axis is chosen correctly.

If you use the stator stamping of a 4-pole motor with four outside grooves for a 6-pole or an 8-pole generator you will probably get no preference positions. The reason is that the flux density in between a coil groove and an outside grooves is less stronger than for a 4-pole generator and that therefore the iron is far from saturation even below the outside groove. The strength of the magnetic flux in a spoke in between the coil grooves will be about the same for 4-pole, 6-pole and 8-pole if the correct magnet size is chosen.

If you would use the stator stamping of a 4-pole motor with 3 outside stator grooves you wil get 12 preference positions but the peak torque will be rather small because only one magnet can be opposite a groove at the same time.
« Last Edit: August 24, 2016, 02:59:28 PM by Adriaan Kragten »

Adriaan Kragten

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Re: Help with motor conversion
« Reply #11 on: August 25, 2016, 04:26:46 AM »
A PM-generator can be made from a 3-phase asynchronous motor if the motor has four, six or eight poles. However, the phase voltage generated at a certain rotational speed is higher for higher pole numbers. If the winding is rectified, you get a DC voltage with only a small fluctuation of the voltage which can be used for 24 V or 48 V battery charging (for rectification see free report KD 340). I prefer a 4-pole motor because this gives the lowest voltage. For a 2-pole motor, there isn't enough place for the magnets to make the armature strong enough.

One can better not use a 1-phase motor. A 1-phase motor can be used in combination with only one phase of the grid but in reality it has a 2-phase winding. The second phase is created by a big capacitor. The main phase winding is directly coupled to the grid. The second phase winding is only used during starting and has a higher resistance than the main winding. This second winding is sometimes disconnected by a centrifugal switch once the nominal rotational speed is reached. If you use a 1-phase motor to transform it into a PM-generator, you should only use the main winding because the starter winding may burn easily. However, rectification of a 1-phase current gives a DC-current with strong fluctuation and this isn't good for the life time of the battery if a load is connected to the battery during charging.

oztules

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Re: Help with motor conversion
« Reply #12 on: August 30, 2016, 05:23:49 PM »
Adriaan,
Do you have any pictures of your 4 pole armature you built for your report KD503.
And do you think it is as effective as the "zubbly" style of conversion (magnets on the surface as compared to your magnets imbedded into the rotor steel)

I have a lot of n50 magnets, and they are too big to use the zubbly method, but may fit into the slots you mention in KD503.

I would like to make a generator that has a inductive reactance current limit built in to prevent burn out in case of over rev, and the fields of that design look to be about right for this application. I have a very large 8 pole French motor picked out for the job, only 3kw nominal, but 8 poles means it is very large comparatively.


.............oztules
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Adriaan Kragten

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Re: Help with motor conversion
« Reply #13 on: August 31, 2016, 02:42:04 AM »
The 4-pole PM-generator as described in report KD 503 has not been built so I have no photo's. However, drawing 1 at page 5 of KD 503 gives a cross section at the middle of the armature and a side view. In the side view you can see that the grooves are making a certain angle with the shaft axis. This drawing and the knowledge about the calculation of the flux density in the air gap as given in chapter 3 of KD 503 must be enough to design your own PM-generator.

There are two ways to mount the magnets in an armature. One way is with radial magnets like done in KD 503 and one way with tangential magnets like done in KD 614.

The option with radial magnets has the following advantages. 1) The armature poles are formed by the remaining material in between the sleeves and the poles are therefore round. This gives a minimal air gap. 2) The magnetic flux, supplied by two rows of magnets is flowing through one pole and therefore the magnetic flux coming out of a pole is concentrated if the pole area is smaller than the total magnet area. This makes it possible to realise saturation of the stator stamping for a 4-pole generator if neodymium magnets are used. For ceramic magnets, saturation can be realised for a 12-pole armature. 3) The magnet grooves can be given an angle such that there is no fluctuation of the sticking torque. 4) During mounting of the armature in the stator stamping, the armature will be pulled against the stator but as the groove depth is a little larger than the magnet height, the magnets won't touch the stator.

The option with radial magnets has the following disadvantages. 1) Rather deep grooves have to be cut and a thin cutter may bend resulting in a groove width which is less at the bottom than at the top. 2) It must be prevented that too much magnetic flux is lost by magnetic short-circuit in between the poles at the bottom of the grooves. This requires a stainless steel shaft or a stainless steen or aluminium bush.

For tangential magnets, a pole is formed by the magnet itself. It is possible to make the north poles by the magnets and the south poles by the remaining material of the armature if the magnets are thick enough. The option with tangential magnets has the following advantages. 1) The grooves which have the be cut in the armature are only shalow. 2) There is no problem of magnetic short-circuit, so the armature and the shaft can be made from normal steel.

The option with tangential magnets has the following disadvantages. 1) Standard magnets are flat and this means that the air gap is maximal and rather large at the hart of the magnet. To minimise the air gap in between the stator and a magnet, the magnets schould be rather slender. So with only one row of magnets per pole, it isn't possible to make a 4-pole armature. 2) If magnets are used for the north and for the south poles, the magnets will touch the stator during mounting of the armature in the stator. So the surface of the magnets will be damagned and this results in corrosion. 3) It isn't possible to concentrate the magnetic flux so a strong armature can only be realised by using neodymium magnets. The option with slender tangential magnets is used in the 34-pole PM generator described in report KD 614.

oztules

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Re: Help with motor conversion
« Reply #14 on: August 31, 2016, 07:55:58 AM »
Thanks for that Adriaan.
If I can get the time I will build this ..... just to see.


.....oztules
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SparWeb

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Re: Help with motor conversion
« Reply #15 on: September 13, 2016, 12:24:49 AM »
Hi BigRock,
Sorry I didn't see this one earlier.  Not getting much time to browse forums these days.

To your question on August 24th: I've done bonding the magnets, and putting screws through them, and both.
I really prefer attaching them with screws.  It guarantees alignment, and they really want to slither and slide around if there's nothing but a flat spot for them.  You don't have to drill the magnets - if you haven't already bought them.  You can get magnets with holes already in the center (KJ Magnetics) and they do cost more but much easier to deal with.

I've summarized my previous Fieldlines posts on my own site: browse and feel free to ask anything you like about them.  You're in a similar spot as I was a few years ago.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

Bruce S

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Re: Help with motor conversion
« Reply #16 on: September 13, 2016, 08:38:53 AM »

I've summarized my previous Fieldlines posts on my own site: browse and feel free to ask anything you like about them.
SparWeb, it might be good to drop your site's link in here somewhere ;-).
Cheers
Bruce S
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SparWeb

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Re: Help with motor conversion
« Reply #17 on: September 13, 2016, 11:38:19 PM »
Hey, right.

Big Rock, it's not well advertised, but all those little icons under our user avatar and location, they do something:  one's a "Private message" link, one's a link to a personal website, one's an e-mail address, one's for the fieldlines user stats, etc...  If you want to see my site it's www.sparweb.ca  or click the green globe under my avatar any time you see a posting.  Several other users have personal websites and it's often interesting to check them out. 

By the way, Oztules, if you ever wrote up a website or blog of your own, I'm absolutely certain that it would be DAMN INTERESTING and you'd make a lot of folks happy.

Mine is not terribly up to date, but the fact is I haven't invented much recently.  Almost finished renovating my garage/shop which means I may have much more to tell in the future!
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

bigrockcandymountain

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Re: Help with motor conversion
« Reply #18 on: September 14, 2016, 09:44:51 AM »
Hello,

Thanks Sparweb.  I've had a good look at your website and it's actually what got me interested in this project to start with.  I was the Derek that emailed you awhile back with questions.  I'm still building a house so this turbine project isn't really happening until next year but once we're living there off grid it will be a priority. 

Do you guys have  a favorite glue?

Any experience with the cheap ebay neo magnets?  They are about $6 CAD shipped for 25mm x 50 mm x 10mm

They don't have holes though.  I might order one just to see what I can do with it.

Thanks

Adriaan Kragten

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Re: Help with motor conversion
« Reply #19 on: September 14, 2016, 10:20:39 AM »
I have good experience with neodymium magnets from the Polish supplier: www.enesmagnets.pl. They have a very large range of rather cheap rectangular and circular magnets. They supply within some days to The Netherlands. I don't know if they supply magnets to America as for air mail, magnets have to be packed such that no magnetic field can be felt at the outside of the package.

SparWeb

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Re: Help with motor conversion
« Reply #20 on: September 16, 2016, 09:41:00 PM »
Hi there!  I remember you now.
You've got time to experiment, so definitely get a few magnets in your hands, if only for the sake of getting used to handling them.

Of course I get carried away with my projects so screw-down magnets and aerospace adhesive are a major over-kill.
If relying on epoxy alone then a few steps for durability: slow cure high-strength high-temp epoxy really is the best because this is a demanding job for an adhesive.
The core of a working generator (or motor) gets hot which softens and weakens the adhesive.  In a generator, the torque comes from the force on the magnets and that push must not break them off the rotor.  The centrifugal force as the rotor is turning is small compared to the magnetic force holding it on, so at least you don't have to worry about that.
You usually need to bond each magnet one at a time.  They tend to slide around on the epoxy if you try to bond too many at once.  They always attract/repel their neighbours.  Get a clamp with plastic over the jaws to hold each magnet in place until the adhesive cures.  You don't have to worry about getting enough adhesive to squeeze out of the joint - the magnetic attraction takes care of that.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

bigrockcandymountain

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Re: Help with motor conversion
« Reply #21 on: September 17, 2016, 10:57:07 AM »
Hello,

So I found some cheap neo's on ebay.  They are 40mm x 20mm x 5mm (close to perfect) with two 5mm countersunk holes.  Could I stack two?  They are $2.20 usd each free shipping.  Might have trouble with them being all magnetised with north toward the countersink.  I have t88 aircraft epoxy.  I think it's fairly low temperature.  Is that ok for glue?  I have lots. 

SparWeb

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Re: Help with motor conversion
« Reply #22 on: September 18, 2016, 08:30:19 AM »
The T88 looks like the good stuff.  The datasheet publishes good strength properties at high temperature, which is what I was talking about.  Sometimes the sales literature is not so clear, and what they might mean is "low-temperature curing" which doesn't need an oven to cure properly (but it helps anyway) which isn't the same as "low temperature strength".  Here we need high temperature strength because of all the heat that builds up in a generator when its running (well, in Canada, some low temp strength doesn't hurt, either!).
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca