20mm x 20mm x 12mm N38 magnets

[vawtwindy]

Finally, will be getting 64 numbers of 20mm x 20mm x 12mm (64numbers) NiCuNi coated N38 magnets, magnetised through thickness.

I have kept ready 12" dia 10mm thickness rotor disks two numbers based on Hugh documents

also  my mind has got deviated with oztules document on awp rework, if i stack two of these magnets in 5mm gap between two of them,(its going to be tough to place at such close gaps), instead of 30 numbers of ferrites, can i use 16

not able to come to a conclusion on pro's and con's of two different methods, most of you have succeeded using hugh's model

can you please guide me through?

ref:
http://www.otherpower.com/images/scimages/5171/awp_1.html
http://www.thebackshed.com/windmill/FORUM1/forum_posts.asp?TID=2812&PN=1&TPN=3

[vawtwindy]

might be i am wrong?

what are all the cons if we can go with radial flux design?

[vawtwindy]

in axial flux

the coils are related to pole like 
8 magnets - 6 coils
12magnets- 9 coils
16 magnets - 12 coils etc.,

is it the similar in radial flux?

[electrondady1]

your question is unclear.
you could place 24 such magnets on a 12" disk.
and use 18 coils for three phase output.
if you are building a dual rotor radial alternator, the ratio of poles to mags is the same for three phase.
with radials it is easier to make overlapping coils and get more copper in. (6 phase ?)

[vawtwindy]

sorry, my apologies for the confusing terms

i intend to ask if i am getting into induction motor conversion, 8 poles (4N, 4S as per attached image), how do i proceed with winding?

3hp induction motor, thats what the shop fella told me, there is no name place, dont have details about its poles..

[ghurd]

The magnet poles must match the motor.
Deciding how many magnet poles to put in before knowing anything about the motor is not a good idea.

If the motor shop is near, I suggest taking it back and asking him the RPM.  It is easy to tell if he can see the coils.
It is not as easy to tell in photos.

Is the motor 3-Ph?
Do you plan to change the coils?
G-

[vawtwindy]

bought it in old metal scrap shop, shop guy was about to break it, luckily i got it, now i feel it is going tobe biggest job, getting the side cover's(bearing hub), etc.,

>>>Is the motor 3-Ph?
yes, it is three phase,

>>>If the motor shop is near,
let me try it taking it to motor winding shops and will try to get the info,


>>>Do you plan to change the coils?
yes, would like to change the coils

[ghurd]

"yes, would like to change the coils"
Count the coil slots in the core.
G-

[vawtwindy]

total 36 slots
each one is about 4.5" length..
inside, ID is 3.5" approx

[ghurd]

For a 1st attempt, might want to keep it kind of basic.

36 slots means 18 coils.
18 coils and 3-ph means 6 coils per phase.
6 coils per phase means 6 magnets.

The 8 magnet rotor is not going to work.

The material the magnets are on is steel, correct?
G-

[vawtwindy]

>>>The material the magnets are on is steel, correct?

Yes, its of steel, close to 18mm thickness

>>>The 8 magnet rotor is not going to work.
Oops, my hurry made it bit complicated, made it with 8 slots, let me try organising the 6 magnets in it.

[vawtwindy]

OMG , i could not do so, do i need to redo the grinding?

any quick approach's>

[Flux]

If you intend to use the original winding you need to establish the number of poles. With no nameplate details you can only get that from the winding .

If you can post a decent picture of the end winding it may be possible to identify it.

If you intend to rewind you have a few options with 36 slots, it's one of the more versatile slot numbers to start with.

If you keep the original winding and your rotor pole count is different from the winding then it won't work.  I find your descriptions hard to follow so I suspect you have little experience of motor conversions.

Motor windings are not of the common type used for axial air gap machines. They are either done as a 2 layer winding or as a single layer with half the number of coils of a 2 layer winding. The maximun number of poles for a 36 slot winding is 12 but the original winding will be 2 , 4 or just possibly 6 pole.

I can't follow what you are intending to do with the 12" discs if you are doing a motor conversion.

If you are looking at a VAWT then I think you have many bigger issues than the alternator itself, I will not comment beyond the alternator.

Flux

[vawtwindy]

>>>If you can post a decent picture of the end winding it may be possible to identify it.
attaching more pictures here.



is the pictures clear?


not sure whether we can use original winding?, looks like we need to go ahead with rewinding, else we might end up in more RPM requirement because of its thinner copper wire.

>>>If you are looking at a VAWT then I think you have many bigger issues than the alternator itself
now doing this for a "hawt"..


sorry for messy "descriptions".

i am parallelly doing axial flux(pretty neat to follow HP book) too,

since i have got 64 numbers of magnets, thought of utilising both the opportunities.

"i landed up in vawts.net and was impressed by "sjh", made me to think of vawt was the reason behind the username i generated here. But alternator is the biggest challenge infront of me".

[Flux]

Pictures are not brilliant but I think it is 2 pole. 

If you are thinking of rewinding then I would suggest you go to 6 or 12 pole depending on how your magnets work out on the rotor for that diameter.

You need to get a layout where the gas between the magnet poles are about half the magnetic width.

If you do it as a 2 pole you will need quite a few of your 20mm blocks per pole but thy are small enough that the curvature shouldn't be too bad.

It should work fine for a HAWT but it will probably only take 8ft blades so you need to be looking at cut in at something like 200 rpm. if you rewind you can do a test winding with 1 turn per pole and wind one phase, that way you get a good idea for cut in. You then choose the biggest wire you can get in.

If you keep the original winding then you have to take what you get or do a lot of messy reconnecting but with 2 pole you don't have much choice, basically star and delta unless it is a multi-voltage winding.

Try to find Zubbly's information, it must still be here somewhere, he gave a great deal of information on motor conversions.

If you do it well it should work out quite well, 3hp is a reasonable size for a first attempt. I am not sure how many of your magnets you can get in there so you probably wont get the same  as if you used all your magnets on an axial and ran it at the same speed but motor conversions are tough and good for high wind areas. Axials are better in low wind areas.

Flux

[vawtwindy]

thanks for your valuable time

"^{6 or 12 pole depending on how your magnets work out on the rotor for that diameter}"

let me try redoing the magnet slots for 6 pole

can we place the magnets this way?

or it should be NN - SS -NN in a row?

>>>"_{You need to get a layout where the gas between the magnet poles are about half the magnetic width}"
was it gas of gaps?

[opo]

For two pole: (it will work with the current winding)

N N N N S S S S
N N N N S S S S

for 4 pole

N N S S N N S S
N N S S N N S S

If you place the magnets as in your picture, you'll get close to zero volts I think.
Cheers.

[Flux]

Sorry that should have been gaps.

I don't really follow your drawing but it certainly looks wrong. for 6 pole you need magnets NSNSNS round the circumference. If you make it with more than one magnet then NNSSNNSSNNSS.  If that rotor on the first picture of the motor is to scale it looks as though you only have room for one magnet per pole round the circle.

When you stack axially the magnets line up.

OPO has the correct idea for two rows of magnets stacked in line. For 3 rows it looks like this.


N S N S N S
N S N S N S
N S N S N S

That is your cylinder flattened out if you follow what I mean.

I think you are confusing pole layouts for radial machines with the layout for an axial where the flux goes the other way.

All magnets within one pole have the same polarity whether they are stacked side by side to increase width or stacked end to end to increase length, just regard them as one big magnet.

Hope this helps, if you can do another sketch we can confirm that you understand. I can't post drawings on this new board.

Flux

[Flux]

I have had another look at your pictures and changed my mind to 4 pole. Difficult to see with all the interconnections and none are good enough to see the slot positions but the last one I think shows enough to confirm it at 4 pole.

It looks burnt out so you are going to need to rewind but at least you have an original winding to look at.

Flux

[vawtwindy]

great, so let me start working towards rewinding it, first let me prepare a test coil then will follow it up, btw for 24v or 48V is there any closeby numbers here?

, since 8pole doesnt work here, i might need to change the octagonal slots to a circular one, and use it for 6 magnets ,

one quick doubt? is it fine, if we mount one magnet on another to make sufficient thickness? eg: NS one pair SN another pair? as attached in picture

[Flux]

You can use 8 pole if your magnets will fit on the rotor but it presents you with challenges if you stick to the single layer concentric winding. It will work on 36 slots if you use the European 2 layer lap winding.

For a motor conversion you will be struggling with space to get enough magnets inside the gap. You will not want to stack magnets in series to increase the thickness. That is fine for air gap machines but with iron cores your 12mm thick magnets are more than adequate. Any attempt to stack one on top the other will reduce the area of the shaft spider to such a low value that you will saturate it and also you will have wide gaps between the poles on the outer circumference which you don't need. As your core will be saturated anyway you will see no benefit from the extra magnets.

Once you decide to go with the motor conversion, read all you can about it from those here who have done it, especially Zubbly's work if you can find it, and I think Sparweb and others have posted information on conversions. Axials are very different and most of the things done with them are not relevent to iron cored machines, If you start reading up the axial stuff and try applying it to a motor conversion you will not be using your magnets to best advantage and you will confuse yourself with the windings. The simple winding scheme used on most axials is never used on radial slotted machines and I wouldn't use them without slots either for a radial but they have advantages for axials where space restrictions are different.

Flux

[ghurd]

Zubbly's papers, and a few more links,
http://fieldlines.com/board/index.php/topic,143568.0.html

G-

[vawtwindy]

thanks Ghurd,

along with this, i have gone through sparweb link too,

let me go through all these links and will get back to this forum.

[vawtwindy]

successfully removed the existing coils

now will start with milling/grinding of the stator part.

i have got one basic doubt now

is there any calculations to ensure how many poles in motor conversions?

[Flux]

is there any calculations to ensure how many poles in motor conversions?

Not sure what you mean by that.  With 36 slots you will not be able to exceed 12 poles and 8 poles will need some thought.

Normally high speed alternators are long and thin with 2 poles or 4 poles.  Low speed alternators are large diameter, short and with many poles. This is ok if you are designing from scratch but you don't have so much choice using an existing core.

Probably the deciding factor will be the best number of Poles you can arrange with your fixed choice of magnet. I seriously doubt whether you can get 12 in but I have not looked closely.  Six may be a possibility or you may find that 4 is possible with more magnet in there.

You must wind the stator for the same pole number as your rotor.  Cores designed for 4 pole will have different slot geometry from those intended for high pole numbers so in many ways you will have to accept a compromise if you convert a high speed machine.

With conversions the big challenge is to get enough magnet in there and when you are not working with the ideal curved magnets the challenge is even greater. With nothing more to go on I think you go for 4 or 6 pole and you can stagger the blocks lengthwise to reduce the effect of cog or you may have enough room to use non uniform spacing for this problem but I don't think you will get much space between magnets to do much in this respect.

Flux

[vawtwindy]

oops, accetp my apologies flux for the miscommunication.

i intend to get clarified on "based on slots how many poles we can derive , so that when i take this motor to the seller and get it exchanged, what could be the slot numbers i need to ask him "


 

[Flux]

Now I am really confused. Having stripped the thing do you want to go back and exchange if for something else? I thought you were going with it.

If I understand correctly, you will have a choice of 24, 32, 36 or 48 slot depending on the type and size of motor. Unless you go very big you will not see much over 48 slots.

24 is normally used on small 2 pole machines 32 tends to be used for single phase. 36 is common and versatile. For larger machines you see 48 , otherwise the slots get big.

Virtually all motors are 2 pole , 4 pole or 6 pole. 8 pole is unusual and anything beyond that very special but all sorts of things exist including dual speed pole change windings.

If you can get 48 it does give you a lot of options right up to 16 pole but the slots will be very deep for a sensible 16 pole winding.

Perhaps you can really explain what you are wanting to do, one minute it is axial then motor conversion and you have a motor which you stripped so this seemed to be the way you are going. Are you trying to fit a motor to your magnets rather than the other way round, I really am confused.

Flux

[JW]

Heres an image of the axial flux alternator configuration, as Flux has mentioned before, the magnetic circuit must be closed.




JW

[JW]

JW

[JW]

Im making these illustrations with bitmap, this one is intensionality drawn this way, to correct for the optical illusion.



JW

[vawtwindy]

"_{I thought you were going with it}."

I will be going with the plan what we were discussing here, the deviation is just because, i broke the side edges of one side cap, the seller told  he will replace the unit itself, but now its fixed by gas welding.

"_{Perhaps you can really explain what you are wanting to do, one minute it is axial then motor conversion and you have a motor which you stripped so this seemed to be the way you are going. Are you trying to fit a motor to your magnets rather than the other way round, I really am confused}.
"
first it is motor conversion.

[Flux]

Thanks for clearing that up, I couldn't read your mind.

In that case you are really back to choosing the best magnet arrangement to decide the number of poles. When you have chosen the rotor arrangement and built it you can do a test winding in your stator to determine the number of turns.

You will probably find a book on motor winding useful but you should be able to sort something out from the links that Ghurd sent you.

You will have to make some sort of inspired guess as to the blade size you intend to use as this will determine the cut in speed. I still suspect it will suit something about 8ft diameter.

Flux

[vawtwindy]

sorry for being so dum....b.., what is 12-10-8 winding?
ref:
http://www.otherpower.com/images/scimages/4/z_conversion_all.pdf