transformer core

[vawtwindy]

Yesterday when i can came across, few small transformers, and on seeing their lamination, i was thinking of using them in axial flux stator

but before starting them, i thought of having your opinion's

i am really bothered about eddy, resistance etc.,,

actually based on sjh's(vawts.net) femm tutorial , i thought of simulating at femm module, unfortunately not able to design them


Attachments

[Flux]

Cores for axial alternators are tricky, there are no readily available cores suitable as most commercial machines are radial.

For a large alternator you could stack a ring of E or U laminations from transformers but you will have a lot of trouble from cogging and you will have iron loss however you do it. Don't even think about cutting up bits of laminations and fitting them in the holes of a conventional axial stator, it will never work on a VAWT and it would be near impossible on a HAWT.

If you are bothered by eddies then one good way to avoid them is not use an iron core, you also need to avoid large section copper wire.

You may or may not be bothered by resistance, obviously too much is a bad thing but unless you have some load matching scheme you will also come unstuck if you have too little. You need the best overall machine efficiency at various wind speeds and if you make the alternator too efficient it will drop your mechanical input power so much that you loose out badly overall.

Instead of modelling alternators it would be better if someone modelled the overall scheme including the blade part of it. Making the best possible alternator may not give you best power out of a wind turbine.

Flux

[Northbay]

what about silicon-iron cores? I could be more specific but I'd need to open my books I just remebr their are made to reduces eddys found in standard iron cores

[joestue]

about the only way to build an axial flux core worth a damn is to start with a toroidal transformer core and get the slots cut with a water jet.
or mill them out and then unwind the strip, debur it and wind it back up.

if you wanted to spend more than a few hundred dollars on this project and could actually get the slots cut, it would be best to buy non grain oriented steel.

you can take 40+ E cores and line them up in a big circle, but for that amount of effort you could just build a more efficient radial machine.

[ghurd]

I ground the welds and separated the individual layers, formed them into a donut around a circle screwed to a piece of plywood.  The bottom (front, against the plywood) looked good, the back showed the individual pieces were not the same dimentions.
It worked pretty well.  Not very hard.  Looked like it would work!

Then I screwed up some of the other (unreplaceable for me) mechanical parts.  It never got finished.
G-

[bob g]

Many years ago, on "fieldlines v1.0"  i laid out a practical design for an alternator
using slotted cored toroids for the stator, it was designed to be a modular system
wherein one could remove and replace individual cores if damaged or to change to
a different winding, or whatever reason.

at the time i set out to find silicon steel to wind my own cores, even cat some from iron
chip, but  i the end i found that there at the time was at least one toroid core manufacture
that could supply such cores as i spec's with the slot cut through and ground to exact airgap specifications as i asked for.

surprisingly the cost was very reasonable, only adding about 40% to the cost of the stock
toroid core.

i never got back to them, or got the time to build the "torogen", but i plan to some day down the road.

having said all that, i am not sure how practical it might be without some sort of electronic transmission, load matching scheme, as the efficiency likely would be quite high, and cogging would be an issue which would have to be carefully worked around to
minimize with proper design.

i have always liked the design from a modular standpoint,  should a coil burn out or short, a single toroid could be removed and replaced, with the rest being left in place.
that could be done up on a tower if the tower is such that it could support a climber
to do the swap.

it might be fun to build a small unit as proof of concept, and to work out a variable flux path idea i also have had kicking around in my head for years, it would basically eliminate cogging and also provide a means of load matching.

bob g

[vawtwindy]

thanks mates.

Now it has cleared a bit in my mind, instead of axial, it would be better if we approach it in radial system. few other members have suggested instead of E core, it would be nicer if we use U core, and the material on core is also plays a vital role,

Iron core or Ferroxcube core,

i have made  a initial sketchup on 12" dia 10mm thick disc, since i have 20mm x 20mm x 12mm N38 in stock thought of using them in this disc.

bit confused on it.. can you please guide me.

[Janne]

Back when I got started with the windpower hobby, my second attempt at making a stator consisted just that.
I cut a big pack of E laminations into strips, that I wound with insulating tape into a backing coil. It was damn lot of work, I think it took over 8 hours to make the backing.
In the end, it worked quite ok, It didn't cog and seemed to conduct magnetic flux quite nicely, but considering the effort, I wouldn't recommend it.
Only way it would make sense, as I see it, would be if you could access a long coil of silicon steel, that you could just wound into a coil without cutting & pasting a million little pieces together.

[Flux]

thanks mates.

Now it has cleared a bit in my mind, instead of axial, it would be better if we approach it in radial system. few other members have suggested instead of E core, it would be nicer if we use U core, and the material on core is also plays a vital role,

Iron core or Ferroxcube core,

i have made  a initial sketchup on 12" dia 10mm thick disc, since i have 20mm x 20mm x 12mm N38 in stock thought of using them in this disc.

bit confused on it.. can you please guide me.

Ferroxcube cores are fine for high frequencies, they have no eddy loss but still have hysteresis loss. The snag is the low saturation level, I have never seen a commercial low frequency alternator design using them, I really can't see the point but I am sure it would work to some extent.

Once you go to radial it seems almost pointless hard work not using common cheap motor cores ( motor conversion), if you want to go the iron cored way. Even if you use the core inside out with magnets on the outside and not bother with the slots it seems better to use the readily available quality core material rather than trying to adapt transformer cores. As Janne showed you can do it but not with the cores in their unmodified state.

You can build a radial machine with a ring of E or U cores but it has many of the undesirable properties of the F & P core. Indeed it can be made to work but to me it seems a step backwards and lots of hard work for zero gain.

Flux

[vawtwindy]

 ???again back to point Blank..

_{cheap motor cores ( motor conversion),}

its pretty much restricted and need to do more machine works for them,if those cores are available separately and you can make a shape out of it it iwll be really good to try,

instead of cylindrical shape, just dreaming of doing the placement of cores as attached image in the beginning of this posting,

[Flux]

I didn't see your attached image, i never do unless someone makes me go and look.

Having seen it, it is just a conventional diagramatic sketch of a big transformer. I don't fokkow what you are trying to do with this in a generator. Are you trying to just include transformers or are you trying to link flux into the core in some way. For rotary things it seems rather strange to be departing from the cylindrical or discoidal shape.

Perhaps I have entirely missed the point, try explaining the idea so that I really understand the question.

Flux

[vawtwindy]

Tried with google sketchup , but it didnt turn out well, google images helped me well to find out appropriate images.

Attached them here,

As per the local lathe guys, these kind of stator teeths are pretty difficult to make and costlier, so my mind went back and tried finding out alternatives.
From then this E-core or U-core idea came up.

now is this img clear ?

[bob g]

if i were you, i would go to ed lenz' site and www.windstuffnow.com

and look up his cast stator core,

although it isn't the perfect stator material, it is however better than an aircore
for the design you are contemplating, probably somewhere between air and a
proper silicon steel core which is going to be very expensive indeed.

any reason what you want to build this design?

the reason i am asking is this,, there has been several years of development and experience  with the aircore for home built alternators, it has proven itself as a very good alternative featuring all the right compromises and few of the faults or problems associated with iron core machines.

this is not to say that an iron core might not be better or more efficient, just that it is much harder and more expensive to do it right, or do it right enough to beat an aircore alternator.  and then even if you are able to build the more efficient alternator, you are left with having to figure how best to drive the thing with blades and wind.

my opinion only, and yours might well vary

bob g

[Flux]

OK I finally managed to open your png file and I see what you are aiming for.

This is in reality one of the most difficult and expensive cores to build properly. No doubt you could get some approximation using U or E cores but you no longer have continuity of the flux round the body of the core.

Personally I can't imagine what virtue this arrangement has over a conventional radial slotted core.I suspect that most other people have also come to this conclusion, the idea seems to keep cropping up in Universities but the thing never gets to a practical device except for some very specialist applications for motors for high density power use such as servomotors. Their requirements are very different from the alternator for wind power.  Many machines need optimum performance at full load or beyond and sometimes schemes like this are needed and for mass production the complexity is justified.

Wind power ideally needs the highest efficiency at least load. The use of any toothed iron core is not the best way to achieve this but if done carefully it can still be a good compromise but I see no reason to abandon the radial construction and make the core design incredibly difficult.

The axial design has several advantages for home construction as long as you keep away from iron cores, the biggest advantage is the ability to alter the characteristics by changing the air gap  so that you can still get a decent match if you are a bit wide of the mark on initial design. It also solves the problem of the costly and difficult to produce core ( by not having one).

If you don't appreciate these real virtues then I see the axial machine as being more trouble than its worth and that is why it failed to survive beyond the end of the 19th century in anything but very specialised fields.

Flux

[vawtwindy]

<sup>if i were you, i would go to ed lenz' site and www.windstuffnow.com

and look up his cast stator core,

although it isn't the perfect stator material, it is however better than an aircore
for the design you are contemplating, probably somewhere between air and a
proper silicon steel core which is going to be very expensive indeed.</sup>

in another forum (vawts.net) he has guided to look at ferroxcube, yes, at windstuffnow i have gathered many of these knowledges, and still not satisfied yet

_{any reason what you want to build this design?}


Whichever be the nearby available material, would like to use them, in someplaces wood is plenty, in one place a student had showed me lots of these E-Core's and asked me whether he can use it, thats when this query came on to me.


(btw, i am a hobbyist, will go to rural colleges/schools help them building small wind turbine using their own hands, but in my expenses_{(since i am spending from my pocket, i am dreaming of reducing the cost on donation)} , i work for an IT org in bangalore, by this two goals i am thinking of achieving, one is the younger generation will understand the importance of electricity once when they came to know about producing it 2, my kids when they grow, they will have some good environment... might be a long process, dont want to get into debate on it )

I do agree many of you have done different experiments and few are really doing better contribution,. so didnt think on re-inventing some nucleus.

[bob g]

please understand, i have no desire to be a "wet blanket" about your design idea,
and have no problems with alternative designs, however

i would direct you to do a google search for this book

Dynamo-Electric Machinery
a manual for student of electrotechnics

by silvanus p. thompson
various editions going back to about 1885 or so

in that book you will quickly learn that there is really nothing new in alternator/generator design, apart from materials used and modern design and engineering techniques that reduce the amount of ancillary materials used and in the process also make things that
are arguably less visually appealing.

in the book you will find sketchs/drawings/plates of all manner of generators and alternators, from the common radial designs to all sorts of axial designs, with steel/iron/laminate and "yes" even the aircore design that is so much in vogue with diy home built wind generators today.

the point being, the air core that is used today, that has become so popular was based on
existing designs that were successful over 100 years ago, but fell out of favor mainly because 99.99% of all alternators/generators were driven by water (wheels or turbines), steam engines, or what they refer to as oil engines (diesel and gas today). all such power sources are of more or less constant speed and stable power, unlike wind power.

had there been more need for wind power at the time, beit because petroleum oil had not
become widely available, or coal not available for steam production, water power limited
we might have today some really massive or at least widely used aircore alternators all over the place.  Wind would have been more viable in a world where cheap fuels were not available.

basically no different that the cyclic interest in wind power over the years, before rural electrification here in the US, folks wanting power bought windgens, after the power lines made it to the farm they fell out of favor. fast forward to the 70's and the oil embargo
we had another spur of interest, and now in the new millenium there is another surge in interest.

 at least this go round some very practical folks like hugh piggot, decided to take
another hard look at what had been done in the past, and what might work better today
given the new neo magnets that were not available in the 30's or 70's.  Apparently he either rediscovered the 100 year old aircores, or learned of them in his research. Either way he from previous experience working with iron cores, radial and axial, likely had
and "aha" moment and could see that the air core removed some if not most of the problems associated with iron core alternators when used with a variable power source such  as wind.

you seem to have much interest in building wind generators, for your local people and family to learn, and  benefit from that power.  therefore, i would strongly suggest
taking a hard look at the history of the alternator/generator and particularly how either
has been used with wind power.

there really is no reason to totally reinvent the wheel, far better to take someone else's
wheel design and work to improve it or alter it in such a way that works best for your application.

bottom line, if you are going to spend money on magnets and copper wire, one is best advised to use those resources in the most practical and advantageous way possible.

best of luck with your project
bob g

[vawtwindy]

Thanks for the book suggestion mate.

_{you seem to have much interest in building wind generators, for your local people and family to learn, and  benefit from that power.  therefore, i would strongly suggest}

No mate, not just wind generators, in some places i preferred just Solar PV's and LED.s

Initially i was just impressed by vawt, but later with fewer modifications vawts are working as small hydels now in streams.

whichever be the possible ways, i am trying to adopt them,

^{at least this go round some very practical folks like hugh piggot, decided to take}

Yes sir, i have a kindle version of his book(PC based kindle app helps in reducing the cost ), and based on it now two of 12v devices are in places apart from 1 hydel.

" not trying to re-invent the wheel" but when it comes on cost, using some available resources would love to use them sir.

approximately for 300watt device i am spending Rs.22000 (indian rupees), in it the 15% goes in for labour charges,
trying to minimise the cost of labour charges will help me saving money and can use them for some other purchase.


"best of luck with your project"
thanks for your wishes sir.

[phil b]

I used a long piece of silicon steel to make the stator on one of my generators.  It does not have groves cut into the steel because I learned there is a fine line there if you don't want cogging. Also, it is destined to be rewound as a toroid later on. It has been in the air quite a while now and will produce 2000 watts easily with a 12 foot dia. blade. I spent a considerable amount of time in its fabrication.

Here's one link on this board.
http://fieldlines.com/board/index.php/topic,138086.0/topicseen.html

[artv]

Hi Phil B,..I liked that link,..I just finished making my core,........but I didn't realize a mag rotor could have such extreme effects (warping).....would this still be a concern using ferrite magnets??.....thanx ....artv

[joestue]

probably not, ferrite magnets only have at best 1/10th the attractive force of neo's

[vawtwindy]

Probably you can try awp machines, in HP site
http://www.scoraigwind.com/Scoraig/index.htm#african

[ghurd]

I ground the welds and separated the individual layers, formed them into a donut around a circle screwed to a piece of plywood. 
G-

Quoting myself. 
Found a pic of it in the old board files.
G-

[vawtwindy]

yeah, i have seen this image dear ghurd, now carefullly organizing the core's, let me update it with images soon.