Author Topic: Rewinding a Proven stator? Hugh?  (Read 27262 times)

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B529

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Rewinding a Proven stator? Hugh?
« on: October 18, 2011, 04:50:39 PM »
Hugh have you rewound a Proven stator? I have shorted WT2500 48 volt stator. As you probably know Proven unfortunately is out of business.

Proven sent me a replacement head a while back, I'm up and running. Would like to rewind the shorted stator just in case.
« Last Edit: October 18, 2011, 04:58:12 PM by B529 »

jlt

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Re: Rewinding a Proven stator? Hugh?
« Reply #1 on: October 18, 2011, 05:04:07 PM »
I to am intrusted In finding more about Proven machines. It seem like a way to make a large turbine using ceramic mags.

scoraigwind

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Re: Rewinding a Proven stator? Hugh?
« Reply #2 on: October 19, 2011, 06:55:22 AM »
I used to wind some Proven stators back in the early 1990s.  The way it worked was that they took a core of lamination strip wound into a ring core (in a spiral).  They put that in a mould and cast epoxy onto it so as to cover sharp edges and to form triangular spacers between the actual coil spaces.  As winders we then put as much wire as we needed onto a bobbin (made of plastic pipe with belled out ends).  We would wind a coil with 28 turns (I think but it was long ago) in fairly heavy wire maybe 1.8 mm or so.  The coil had two layers and there was exactly the right amount of space.  We soldered the tails of the coils.  Then the stator got cast again in epoxy to set the whole thing.

So it is doable but not simple.  I understand that Kingspan have bought Proven http://scoraigwind.co.uk/?p=1038

I suppose they might be able to supply spares.

Proven adopted the toroidal design back in about 1992 (it's a classic design by faraday or the like - flux will know I am sure) and it has served them well.  It's basically a flux concentrator that takes the flux from two large poles one on each side of the core and feeds it through the coils along the core which has much smaller area, so much higher flux density.  It's a pretty good way to use ferrites.  They glued them onto steel disks using a flexible acrylic adhesive.  Now they put hoops on.

This is not an easy design for homebrew.
Hugh Piggott scoraigwind.co.uk

Flux

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Re: Rewinding a Proven stator? Hugh?
« Reply #3 on: October 19, 2011, 07:27:57 AM »
This is an interesting post. The earliest dynamos ( Gramme ring) were a form of torus winding, they were radial and only used one side but the axial version lets you have flux entering from both sides. It has a lot of advantages and gives a winding with the minimum amount of interconnecting copper, it also is one of the few methods of winding a full 3 phase winding without overlapping coils.

As Hugh said, it is a tricky one to make and although in theory it is easy to wind, it is rather laborious to do by hand. There are clever toroidal winding machines used in the mass production of toroidal transformers but would probably not help a lot here with a polyphase winding.

Problems to solve are holding the core rigid so that magnet pull doesn't displace the strip, insulating the core with its sharp edge, making some means of positioning the individual coils and then finally mounting the whole stator assembly within the rotating field on each side.

Back to the original question, if the thing is fried it will need a complete rewind and the messy bit will be removing the old winding without damaging the core and its insulation and coil supports.

If it is only a local coil fault and not burnt generally you should be able to replace one or several coils without having to strip the whole winding.

You should easily be able to find the shorted coil by energising one phase of the stator with ac ( magnet assembly completely removed), the shorted coil will heat up quite quickly just like a shorted turn on a transformer. In fact the winding is very much like a variac for those familiar with such things.

I should point out that the flux path during this testing method id very different from the flux path when working within its magnetic field.

Flux

B529

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Re: Rewinding a Proven stator? Hugh?
« Reply #4 on: October 19, 2011, 08:09:51 AM »
Hugh, thanks for the reply and description of how the stator is constructed. I didn't know Kingspan bought out Proven, that's good news as I have installed 4 WT2500's.

I have access to a motor shop. I intend to bake/melt off the epoxy in their oven and go from there.  Before baking the stator, I'll make a mold for it.

This will be a winter project, I'll snap some pictures along the way. 1st move is getting off the rear magnet disc, I'll fabricate a bracket/puller that will use a hydraulic bottle jack to pull off the rear magnet disc.

jlt

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Re: Rewinding a Proven stator? Hugh?
« Reply #5 on: October 19, 2011, 10:02:34 AM »
   Are the rotors laid out the  same as a axial rotor.   And what is the coil to winding ratio?  Also  is there a diagram of the winding .

scoraigwind

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Re: Rewinding a Proven stator? Hugh?
« Reply #6 on: October 19, 2011, 08:54:15 PM »
The rotors look similar to one of my dual rotor axials except that there are 2 north poles looking at each other (across the core) and 2 south poles looking at each other as you go around, instead of north looking at south.  The flux from the 2 norths goes into the core and re-emerges at the 2 south poles.  So it's actually a very different flux path.
Hugh Piggott scoraigwind.co.uk

SparWeb

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Re: Rewinding a Proven stator? Hugh?
« Reply #7 on: October 20, 2011, 01:09:55 AM »
I needed some pictures to follow this discussion.  Here are a pair taken from a MREA workshop (maybe by DanB):





The link (halfway down the long page)   http://www.buckville.com/drupal/wisc_2010
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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Warrior

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Re: Rewinding a Proven stator? Hugh?
« Reply #8 on: October 20, 2011, 06:24:00 PM »
Here's a picture of the stator without resin....I do wonder how the coils are wound if the core is a single loop  ???

Why can't Murphy's Law be used to my advantage?

B529

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Re: Rewinding a Proven stator? Hugh?
« Reply #9 on: October 20, 2011, 08:54:09 PM »
Warrior, thanks for the picture.

Hugh, are the triangle spacers formed/molded from the initial epoxy coating? 

scoraigwind

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Re: Rewinding a Proven stator? Hugh?
« Reply #10 on: October 21, 2011, 03:15:39 AM »
Yes the triangles are moulded when the core is put in the first mould.  They are enormously helpful for keeping the coil shage and they also allow a bit of free space in the circumference for bolts to run into the stator in some cases. 

winding the coils means passing a bobbin of wire repeatedly through the hole and pulling tight.  The coils are small so you don't need a big bobbin.  Then the coils are connected in phase groups.  You have to reverse every second coil so as to get the correct phase angles.
Hugh Piggott scoraigwind.co.uk

artv

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Re: Rewinding a Proven stator? Hugh?
« Reply #11 on: October 21, 2011, 04:32:58 AM »
Hi All,....Hugh you say the rotor the magnets are n-n ,s-s and so on ,and that the coils are reversed every other connection,thats seems like you could just put the poles n-s, n-s and not reverse the coil connections??
In Warriors' pic there are 36 coils ,so does that mean 48 magnets per side?...
When you were winding did you do each coil individually, or could you wind every other coil, since they get connected the same??
Very interesting thread .....thanks B529 .......artv

scoraigwind

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Re: Rewinding a Proven stator? Hugh?
« Reply #12 on: October 21, 2011, 05:46:27 AM »
Hi All,....Hugh you say the rotor the magnets are n-n ,s-s and so on ,and that the coils are reversed every other connection,thats seems like you could just put the poles n-s, n-s and not reverse the coil connections??
No, you really don't get the geometry.  There is a core in the middle of the coils and the two magnets feed flux into this core.  it passes along the core tot he next magnet-pair.  Opposing magnets would be very happy but the flux would not pass along the core through the coils so you would get nothing.
Quote
In Warriors' pic there are 36 coils ,so does that mean 48 magnets per side?...
When you were winding did you do each coil individually, or could you wind every other coil, since they get connected the same??
Very interesting thread .....thanks B529 .......artv
There are 3 coils per magnet.  So this would have 12 poles.

YOu wind all the coils, and then connect them in phases (1-4-7-11... for example), taking care to reverse the connections to every second coil.
Hugh Piggott scoraigwind.co.uk

Flux

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Re: Rewinding a Proven stator? Hugh?
« Reply #13 on: October 21, 2011, 05:56:03 AM »
Artv

This is a conventional 3 phase winding and things are a bit different from the usual windings here.

A 3 phase winding needs an electrical displacement of 120 deg but if you take 3 adjacent coils  as your 3 phases they have a 60 deg electrical displacement. This is often the most convenient way to wire things and it is  just a case of reversing the connections to the middle phase to bring it right.

No messing about with the magnet system will do any good. If you use every third coil as the phase starting point then there is no need to reverse anything but your star point no longer comes from the 3 adjacent coils. Either method works and you choose the most convenient physically.

There is very little on here that will help you understand conventional windings, the single layer windings used for the axials work the same way but the coil numbers and connecting methods are different.

Flux

Flux

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Re: Rewinding a Proven stator? Hugh?
« Reply #14 on: October 21, 2011, 06:14:58 AM »
There are two differences from the single layer winding I covered one but Hugh was talking about the other.

In this winding you have the same number of coils as magnets for each phase ( 3 times total). As each magnet is of opposite polarity so the volts of adjacent coils will be reversed. To make them add you need to reverse every second coil ( in that phase).

When you have the phases right then you have to consider the other issue I replied to first.

Flux

SparWeb

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Re: Rewinding a Proven stator? Hugh?
« Reply #15 on: October 21, 2011, 01:58:35 PM »
Then the Proven dual stators repel each other when assembled, don't they?

I think more understanding of this alternative would be very beneficial to the group.

The NEO magnet prices aren't going down any time soon, and we may find ourselves moving back to ferrite blocks and laminated-core alternators in the future.

As Hugh mentioned, this is an effective way of concentrating flux delivered by a weaker (ferrite) magnet to achieve a high flux density. 
I can't see a severe source of cogging in the design.
Mounting the stator is not obvious to me yet, and the weight is much higher than the Neo axials (pounds per watt, so to speak).

If I get some free time, I expect I will find myself researching these configurations a little more.
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
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Flux

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Re: Rewinding a Proven stator? Hugh?
« Reply #16 on: October 21, 2011, 02:58:03 PM »
Yes without the stator the rotors repel, With the stator present both rotors attract the stator core.

Bear in mind that the coils are at right angles to what you would find on an axial, there would be no output without the torus no matter whether the magnets attract or repel.

Consider one magnet rotor for now, flux passes from N across the air gap to the core and passes through the core to the next air gap and S magnet. It is the flux passing through the core over which the coil is wound that links the coil. You can add a second rotor on the other side with the same polarity, flux then links from both magnet circuits, the flux in the core is doubled and twice the flux links the coil so you only need half the turns.

It's not a flux concentrator in the normal sense and doesn't increase the flux density in the air gap but it does let you feed two lots of flux through the coil. The coil flux  is concentrated ( doubled) but the actual magnet flux density in the air gap is not changed.

Halving the turns gives the possibility of 1/4 the resistance. The other big factor is that the low flux from ferrite magnets can be carried by quite a thin torus so the wire length can be much shorter than a conventional coil wound in the normal way. The third factor in its favour is that you can wind the coil as a thin layer in good thermal contact with the core, cooling is excellent with the magnest fanning the air gap.

You are absolutely right that it poses a few interesting mechanical challenges, mounting the stator being one of them. The magnetic pull is basically balanced but it is not during assembly so your structure needs to be fairly strong. It is nothing like as bad as a single rotor axial with laminated core, that's a mechanical nightmare.

Strange how things come in cycles, i mentioned the torus many times in the past but no interest ever happened, now everyone is looking at it.

Flux

bob golding

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Re: Rewinding a Proven stator? Hugh?
« Reply #17 on: October 21, 2011, 05:54:35 PM »

Strange how things come in cycles, i mentioned the torus many times in the past but no interest ever happened, now everyone is looking at it.

Flux
[/quote]

i blame the chinese. they might have shot themselves in the foot though,by  jacking up the price of neodymium. read they are stopping production for a month to stimulate the price.

if i cant fix it i can fix it so it cant be fixed.

rossw

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Re: Rewinding a Proven stator? Hugh?
« Reply #18 on: October 21, 2011, 06:34:19 PM »
Halving the turns gives the possibility of 1/4 the resistance.

OK, I've missed something. Surely halving the turns gives 1/2 the resistance, but 1/4 the *power loss* ??

kevbo

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Re: Rewinding a Proven stator? Hugh?
« Reply #19 on: October 21, 2011, 06:51:26 PM »
Half as many turns take up 1/2 the volume, so you can use wire with twice the cross section.  Along with half the length, this gives 1/4 the resistance.

bob golding

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Re: Rewinding a Proven stator? Hugh?
« Reply #20 on: October 21, 2011, 07:59:02 PM »
Then the Proven dual stators repel each other when assembled, don't they?

I think more understanding of this alternative would be very beneficial to the group.

The NEO magnet prices aren't going down any time soon, and we may find ourselves moving back to ferrite blocks and laminated-core alternators in the future.

As Hugh mentioned, this is an effective way of concentrating flux delivered by a weaker (ferrite) magnet to achieve a high flux density. 
I can't see a severe source of cogging in the design.
Mounting the stator is not obvious to me yet, and the weight is much higher than the Neo axials (pounds per watt, so to speak).

If I get some free time, I expect I will find myself researching these configurations a little more.


found these people who seem to do one offs for those in the USA.

http://www.alphacoredirect.com/contents/en-us/d140.html

there largest core is 67 dollars and might be big enough for  some experiments at least. could be unwound and made larger. i just remembered i have a couple of dead variacs around somewhere so will see what i can do with them when i can find them.
if i cant fix it i can fix it so it cant be fixed.

rossw

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Re: Rewinding a Proven stator? Hugh?
« Reply #21 on: October 21, 2011, 07:59:46 PM »
Half as many turns take up 1/2 the volume, so you can use wire with twice the cross section.  Along with half the length, this gives 1/4 the resistance.

Ahh, that was the missing bit.  Half the turns *and* twice the CSA.

phil b

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Re: Rewinding a Proven stator? Hugh?
« Reply #22 on: October 21, 2011, 08:29:28 PM »
Sparweb, I couldn't stand it as long as you could. Here's the first bit of research I found on Google.
http://dspace.mit.edu/bitstream/handle/1721.1/18013/57205740.pdf?sequence=1

I fully intended to make the 'iron genny' a toroid when I  built it in 2007. http://fieldlines.com/board/index.php/topic,138086.0.html
 It lasted until a tornado took it out of the air last May.  :-\



« Last Edit: October 21, 2011, 09:46:24 PM by phil b »
Phil

oztules

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Re: Rewinding a Proven stator? Hugh?
« Reply #23 on: October 21, 2011, 09:58:32 PM »
"Strange how things come in cycles, i mentioned the torus many times in the past but no interest ever happened, now everyone is looking at it."

Yes, talking about them and seeing pictures so we can fully understand it are two different things.

Flux (magnetic) was cheap, but now it's not, so easy alternators with cheap flux are no longer a cheap easy alternative. This means to get a decent unit, we need to do less of the easy, an more of the cheap.....

Chris has stimulated the ferrite idea, as he has shown that real power is a possibility. ( I can't stand the thought of rpm increasing devices 24/7) Now this torus type of alt promises sensible flux usage, and the possibility of decent power in a direct drive.... it has to inspire something.

I'm currently eyeing off a stack of microwave transformers. The "I" parts may lend themselves to messy, but useful stator plates. The short spans will create lots of reluctance, but even with myriads of end to end gaps (very tiny ones)... it may still be worth it.

Fixing the stator may not be that difficult if we use the fibreglass to protrude out the ends of the "triangular lands".... we could have 36 fixing points if we desire.

For folks in the states (USA) then south of the border  is this   http://www.villaindustrias.com/catalogos/siliconsteel.html

For  rule of thumb, what is the thickness of the steel stator. If I try this it will be 12mm or so (transformer lamination dependent)  I assume the magnet covers three coils....




.................oztules
Flinders Island Australia

phil b

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Re: Rewinding a Proven stator? Hugh?
« Reply #24 on: October 21, 2011, 10:34:18 PM »
Off topic...I tried the link Oztules. Avast reports malware on the site.
Phil

ghurd

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Re: Rewinding a Proven stator? Hugh?
« Reply #25 on: October 21, 2011, 10:41:46 PM »
"Strange how things come in cycles, i mentioned the torus many times in the past but no interest ever happened, now everyone is looking at it."

Yes, talking about them and seeing pictures so we can fully understand it are two different things.

Flux (magnetic) was cheap, but now it's not, so easy alternators with cheap flux are no longer a cheap easy alternative. This means to get a decent unit, we need to do less of the easy, an more of the cheap.....

Chris has stimulated the ferrite idea, as he has shown that real power is a possibility. ( I can't stand the thought of rpm increasing devices 24/7) Now this torus type of alt promises sensible flux usage, and the possibility of decent power in a direct drive.... it has to inspire something.

I'm currently eyeing off a stack of microwave transformers. The "I" parts may lend themselves to messy, but useful stator plates. The short spans will create lots of reluctance, but even with myriads of end to end gaps (very tiny ones)... it may still be worth it.

Fixing the stator may not be that difficult if we use the fibreglass to protrude out the ends of the "triangular lands".... we could have 36 fixing points if we desire.

For folks in the states (USA) then south of the border  is this   http://www.villaindustrias.com/catalogos/siliconsteel.html

For  rule of thumb, what is the thickness of the steel stator. If I try this it will be 12mm or so (transformer lamination dependent)  I assume the magnet covers three coils....

.................oztules

I think several of us posted ideas based on torrids, and even stacking/aligning microwave transformers.

Ed's stuff may be simpler for most of us.  Free magnets, free laminate material, sometimes free wire.  That makes it cheap!

30" diameter, 14MPH, 20W.  170W in 30MPH wind.
http://www.windstuffnow.com/main/microwave_wind_generator.htm

Ed's overlapping coils on an un-slotted core of laminations may be of interest too.
It uses neos, but the design could be adjusted for cheap magnets.
http://www.windstuffnow.com/main/alt_from_scratch.htm

G-
www.ghurd.info<<<-----Information on my Controller

oztules

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Re: Rewinding a Proven stator? Hugh?
« Reply #26 on: October 21, 2011, 11:45:21 PM »
Sorry Philb and anyone else with windows. I don't use it, so I don't use a virus/malware thinggy. (Linux has clam antivirus, but it has not picked it up as a threat to linux) Odd a commercial site has malware?

Ghurd,
The microwave laminates I am thinking of, is to use the "I" ones as a "continuous strip," and then coil it up....... in reality, make a round mould and then feed them in one at a time and bend them to suit the radius. We should end up with the same thing for free.... bit like using strip steel for the Seeley  magnet drum.... silly till you try it.

Using the trannies for a regular drum type would work, but just feels coggy in theory..... when you use Neo, you don't need to do it. That said, the AWP that Hugh designed is still the best in my eyes.... especially for the reactance limiting.... makes it burn proof. Will do 1.5kw all day without any one worrying.... even if it over speeds sometimes.

Ed still didn't use the advantage of the torroid.... .. and that is small air gap.  He< does/did have 80 lbs of silicon steel strip, but it was 3/4" I think. He<only used it for backing on a stator though I think/recall.

It is the only way..... other than the radial fancy stamped iron  stator to get half decent flux to link the coils....... that I know of. We need to talk kilowatts with ferrites if were going to do better than Chris has already done with  poor flux circuit and speed.




.............oztules
Flinders Island Australia

Flux

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Re: Rewinding a Proven stator? Hugh?
« Reply #27 on: October 22, 2011, 04:46:08 AM »
Yes you should be able to do it with microwave transformer strips. If you have a guillotine you could also cut the legs off the E lams.  With care bedding them down you could epoxy one ring at a time and clamp it tight to get a nice tight curvature. with a bit of practice you may be able to do several rings at a time if you can keep the joints fairly close together.

It will work better with long narrow magnets and that means a fairly thin but very wide torus ( lots of time sticking plenty of stripe to get a decent size core. At least the transformer steel will be much better than using crap strip or wire so it will likely justify the effort.

Keep the flux density in the core below 1.5T and idea ll lower than that if you want low core loss for low wind start up. When you consider that you only have about 0.3T on either side you will find that with nice long narrow magnets the core can be quite thin. If you go for short wide magnets you will not get the flux density up in the core high enough to benefit from the shorter turns.

Flux

oztules

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Re: Rewinding a Proven stator? Hugh?
« Reply #28 on: October 22, 2011, 05:33:43 AM »

Sorry Flux/Hugh/anyone else that knows..... but I know little of this style of alt.

Some parameters / rules of thumb would be handy if we/ me/someone is going to try this.

magnet width versus no of coils to span?

I suspected that a magnet would have to span 3 coils is this right?.... ie for a 36 coil unit, we need 12 magnets.

Stator thickness will be laminate thickness dictated by the transformer... maybe 12mm... so that's fixed.

Flux's statement of long and narrow makes it hard to see how the mags are three coils wide, can anyone expand on this please?

If we used (eg,) 36 1inch wide coils, then 3 coil span is 3".... what size magnet width would you suggest (assume 1" thick). Does this mean 3" wide magnets by say 3" long?


Just need some direction that I have not been able to glean thus far.






..................oztules

Edit Yes Flux, that is the idea exactly.
It will be simple to do (like most of my ideas), will Just take patience and time. It will build a successful stator I suspect.... now how to use it?
« Last Edit: October 22, 2011, 07:12:53 AM by oztules »
Flinders Island Australia

artv

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Re: Rewinding a Proven stator? Hugh?
« Reply #29 on: October 22, 2011, 06:43:30 AM »
Hi Everyone ,...I already have a core from my first build it was made from 28 or 26 guage roofing steel which is coated both sides to prevent rusting. The size is 5.5" inside dia. ,7.5" outside by 3/4" thick,
Would like to give it try ,....think this steel would be suitable??
Thanks .....artv

B529

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Re: Rewinding a Proven stator? Hugh?
« Reply #30 on: October 22, 2011, 07:02:22 AM »
Sorry Flux/Hugh/anyone else that knows..... but I know little of this style of alt.

Some parameters / rules of thumb would be handy if we/ me/someone is going to try this.

magnet width versus no of coils to span?

I suspected that a magnet would have to span 3 coils is this right?.... ie for a 36 coil unit, we need 12 magnets.

Stator thickness will be laminate thickness dictated by the transformer... maybe 12mm... so that's fixed.

Flux's statement of long and narrow makes it hard to see how the mags are three coils wide, can anyone expand on this please?

If we used (eg,) 36 1inch wide coils, then 3 coil span is 3".... what size magnet width would you suggest (assume 1" thick). Does this mean 3" wide magnets by say 3" long?


Just need some direction that I have not been able to glean thus far.






..................oztules

I'll try to get the rear magnet rotor off next week and post pictures.

Flux

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Re: Rewinding a Proven stator? Hugh?
« Reply #31 on: October 22, 2011, 10:01:38 AM »

"Sorry Flux/Hugh/anyone else that knows..... but I know little of this style of alt.

Some parameters / rules of thumb would be handy if we/ me/someone is going to try this.

magnet width versus no of coils to span?

I suspected that a magnet would have to span 3 coils is this right?.... ie for a 36 coil unit, we need 12 magnets.

Stator thickness will be laminate thickness dictated by the transformer... maybe 12mm... so that's fixed.

Flux's statement of long and narrow makes it hard to see how the mags are three coils wide, can anyone expand on this please?"


I missed a lot of this. Can I start with a conventional 3 phase radial winding as it is clearer.  A single phase winding has as many coils as poles. Let#s take a 12 pole case.

It will have 12 poles as a single phase winding. Now introduce another 2 phases to fill the gaps of the single phase winding, you now have 36 coils. For a star winding the output is from two series connected phases, they add as root 3 and the rectifier will ignore the other phase at any instant. it makes sense for the magnets to span 32 of the 3 coils and it is conventional for a machine to have poles spanning 2/3 of a pole pitch. ( this also works well for single phase as distributing it over 2/3 of the winding space is again near optimum, winding more put a lot of turns so far out of phase that they mainly contribute resistance.

OK so far?    This is all good theoretical stuff and makes good use of material but you can squeeze more out by increasing the magnet pole width even more even if it puts the magnet cost a bit.  You will know this if you are familiar with the AWP, the poles are crammed in to the point where they touch  and it works fine.

Now an axial really needs sector shaped magnets to be anything like correct, so bearing in mind what we have just covered i suspect the nest you can do with a torus is make your magnets touch at the inner radius. I suspect proven actually have a gap but I can't see the gap helping much.

So for 12 poles you have 36 coils. I would think your 12mm thick core would be ideal for 1" thick magnets you won't saturate the coil and the thin core keeps the turn length to a minimum.

I also came to the conclusion that you extend the coil spacer bars for stator fixing and you wouldn't need 36 of them.

Another point that came up somewhere, NO it doesn't cog.  There will be iron loss drag that might be a small issue on start up but not as bad as any form of slotted core.

This is one of the simplest designs to get a lot of magnet area working on a small length of copper and I suspect it will be better than mounting ferrite blocks edgeways and using conventional flux concentrators on the poles.

Will it reactance limit? I don't know, it probably will but it may not be within the working coil temperature limits. I am not sure how the leakage flux will be influenced by armature reaction. Does anyone know if the Proven shows any signs of this?

Hope that gives you a starting point. The designs that this is based on in the 1870's were single phase and with wound magnet poles ( cramping magnet poles in that case caused serious flux leakage but ferrite won't behave the same).

Flux

If we used (eg,) 36 1inch wide coils, then 3 coil span is 3".... what size magnet width would you suggest (assume 1" thick). Does this mean 3" wide magnets by say 3" long?

Flux

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Re: Rewinding a Proven stator? Hugh?
« Reply #32 on: October 22, 2011, 10:05:15 AM »
Typo here that may cause confusion.

"It will have 12 poles as a single phase winding. Now introduce another 2 phases to fill the gaps of the single phase winding, you now have 36 coils. For a star winding the output is from two series connected phases, they add as root 3 and the rectifier will ignore the other phase at any instant. it makes sense for the magnets to span 32 of the 3 coils and it is conventional for a machine to have poles spanning 2/3 of a pole pitch. ( this also works well for single phase as distributing it over 2/3 of the winding space is again near optimum, winding more put a lot of turns so far out of phase that they mainly contribute resistance."


That should read:- It will have 12 coils as a single phase winding.

Sorry

Flux