Author Topic: Radial Flux Generator Project  (Read 92864 times)

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jimovonz

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Re: Radial Flux Generator Project
« Reply #33 on: July 17, 2010, 07:22:47 AM »
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But if I place the horseshoe magnet on the inside of the ring it'll hold a nail to the outside of it.
Isn't this a bad thing? If I get you correctly, you held a horseshoe magnet with both poles in contact with the inside of the ring? Shouldn't this 'short out' the flux between the poles through your ring, leaving nothing on the outside to effect the nail? Seems to me that this indicates the material is saturated - surely to get even worse when using NdFeB (which I presume the horseshoe is not). Much like the paperclip test on the back of the magnet rotors in a dual rotor axial.

TomW

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Re: Radial Flux Generator Project
« Reply #34 on: July 17, 2010, 07:49:46 AM »
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But if I place the horseshoe magnet on the inside of the ring it'll hold a nail to the outside of it.
Isn't this a bad thing? If I get you correctly, you held a horseshoe magnet with both poles in contact with the inside of the ring? Shouldn't this 'short out' the flux between the poles through your ring, leaving nothing on the outside to effect the nail? Seems to me that this indicates the material is saturated - surely to get even worse when using NdFeB (which I presume the horseshoe is not). Much like the paperclip test on the back of the magnet rotors in a dual rotor axial.


Jim;

Do not mistake me for an expert or a builder but...

In an iron core I think you want it to be saturated?

It seems right to me but I never tried it.

Seems you want as much flux in the core (saturated) as possible.

I will shut up now.

Very nice looking core, Chris! Truly.

Tom

joestue

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Re: Radial Flux Generator Project
« Reply #35 on: July 17, 2010, 07:52:51 AM »
there won't be much eddy current, but the iron may saturate behind the hole.
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tecker

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Re: Radial Flux Generator Project
« Reply #36 on: July 17, 2010, 10:06:15 AM »
IF the mags are large enough there will be saturation the plastic will get hot and the whole Nine . Got a Tee shirt for this one .  Bake it to see if it will deform . If it does just put your coils on a steel ring . The ring works, will not cog and have good magnet directions . I think Flux did this awhile back I use a lot of Ceiling fans for cheap alternators  I have a ring with coils on one at a barn it's still there . Just cast in your winders no steel on the ring to manage the radius .
  My over heating experience was with coils that had hot spots and shorted . Good luck I hope your mix was good and this project goes forward for you .
« Last Edit: July 17, 2010, 10:09:33 AM by tecker »

frepdx

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Re: Radial Flux Generator Project
« Reply #37 on: July 17, 2010, 11:43:39 AM »
Interesting.... You know Electromagnetic Plastics are the next big thing...

Somaloy has been around for a while. It has to be pressed at 40,000+ psi and then sintered, but it's good stuff.

ChrisOlson

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Re: Radial Flux Generator Project
« Reply #38 on: July 17, 2010, 12:14:19 PM »
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But if I place the horseshoe magnet on the inside of the ring it'll hold a nail to the outside of it.
Isn't this a bad thing? If I get you correctly, you held a horseshoe magnet with both poles in contact with the inside of the ring? Shouldn't this 'short out' the flux between the poles through your ring, leaving nothing on the outside to effect the nail? Seems to me that this indicates the material is saturated - surely to get even worse when using NdFeB (which I presume the horseshoe is not). Much like the paperclip test on the back of the magnet rotors in a dual rotor axial.

Well, I don't know for sure.  Using the powdered iron is an experiment to see if a core can be built from commonly available materials (iron powder from a brake lathe at the tire shop and fiberglass resin for binder) and still get decent performance from the magnets used.  There's a lot more exotic materials that could be used like laser cut laminated low-loss electrical steel plates.  But using the more exotic and expensive materials would negate one of my purposes here - to build a decent performing radial generator that the average person can build without spending and arm and leg on materials.

Flux flows or moves better thru iron than open air from the north pole to the south pole.  With the horseshoe magnet the flux is traveling from pole to pole thru the open air and it wouldn't pick up the nail at a distance of 1.5".  Iron can direct magnetic flux, and the test with the nail told me that the iron is directing the flux thru the core from the north pole to the south pole so the lines of flux can be cut by the coil windings as the rotor rotates.  If the magnetic circuit thru the core was open it wouldn't work.

The test with the paperclip on the back of an axial rotor serves a different purpose.  There you're using steel plates to direct flux thru the air gap and you don't want flux on the back side of your plates where there's no coil windings.

I didn't have time to look at this thing this morning but then a sudden realization hit me about a design flaw I have here - I wanted to use a delta winding in this so I could wind it with smaller wire.  But I'd have to go to a 12/36 to do that so the rotor poles and coil legs are spaced at 30 degrees.  With the 12/18 the coil legs are spaced at 40 degrees, the poles at 30.  This is not good for a delta winding so at this point I have two choices - wind it star or cut 18 more teeth into it and build a 12/36.

I hate the thought of the 12/36 because one, it's a lot of extra work, and two the winding then becomes non-trivial and something the average person is not going to be able to do.  I built a 12/36 axial once and it took two days to wind it.

I'm going to have to lay this thing aside and go do something else while I mull this over.....
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Rover

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Re: Radial Flux Generator Project
« Reply #39 on: July 17, 2010, 12:27:01 PM »
Why not just wire as you intended ,  rectify the phases and see where you are at? I'm thinking you have a lot of variablles going on , might be too early to make a star/delta decision
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Rover

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Re: Radial Flux Generator Project
« Reply #40 on: July 17, 2010, 12:41:12 PM »

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iron powder from a brake lathe at the tire shop and fiberglass resin for binder

Just curious, how certain are you that the powder is all iron, I'm assuming this is a rotor lathe , there are quite a few aluminum rotors
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ChrisOlson

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Re: Radial Flux Generator Project
« Reply #41 on: July 17, 2010, 12:55:32 PM »
Just curious, how certain are you that the powder is all iron, I'm assuming this is a rotor lathe , there are quite a few aluminum rotors

The stuff I got had everything in it, from aluminum chips, to dirt off the floor, lead wheel weights, cigarette butts, screws, you name it.  I sifted it thru a window screen to remove the big chunks.  Then I put a pile of the stuff on a piece of plexiglass, and using a horseshoe magnet underneath the plexi, moved the magnetic material from the impure pile to a new pile by making "sweeps" with the magnet.  When I got a pile of pure iron I brushed it off the plexi into an empty ice cream bucket.

It was a little time consuming but I got the stuff for free.  Otherwise you can buy iron powder online in various micron sizes for something like $40 for 5 lbs.  It took about 10 lbs of iron to make this core and after machining it weighs 8.4 lbs.
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Rover

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Re: Radial Flux Generator Project
« Reply #42 on: July 17, 2010, 01:03:18 PM »
Hehehe awesome. a lot of work for a pile of iron dust... but cool. I've been following this thread wiith a lot of interest, thinking about doing my own radial.  (I have quit e a bit of experience with epoxies, but no milling/lathe stuf) , so typically most of the stuff I fab is glass/kevlar/fiber  under vacuum when I can. Guess that is what peaked my curiosity on you project.

Kudos
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ChrisOlson

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Re: Radial Flux Generator Project
« Reply #43 on: July 17, 2010, 01:19:13 PM »
Why not just wire as you intended ,  rectify the phases and see where you are at? I'm thinking you have a lot of variablles going on , might be too early to make a star/delta decision

IRP is certainly an option but I only wanted three wires coming down the tower because the turbine this thing is going to be tested on has wire buried underground from the tower and there's only three wires buried.

Winding delta is easier than winding star because you can use more turns of smaller wire and get a better "pack" in the coils.  If I built a coil winder to fit this thing and wound the coils off the stator, as opposed to hand winding them on the stator, then poke them in the teeth similar to the way electric motors are rewound, it wouldn't be all that bad.  But when you hand wind on the stator using the heavy wire required with star you have to make a wooden "poker" out of a piece of dowel because when you make a wrap it tends to want to bow after it goes around the corner.  So you have to use the "poker" to bend the wire tight to the other wraps.

If I would go to six poles instead of 12 the timing would be right for delta but then the amount of wire in the winding head gets excessive.  Plus anytime you have the same number of coils in one phase as you have generator poles, every other coil in each phase has to be wound backwards.

I hate to make too many compromises for ease of construction and give up performance capability.  There's no doubt 12/36 would be the ultimate in performance with the least internal resistance due to less wire used in the winding heads.  I just got done winding a test coil on it a bit ago.  I have to unwind it and measure the length of wire in one coil.  When I know that, I can do some calculations to see how each configuration comes out for internal resistance.
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ChrisOlson

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Re: Radial Flux Generator Project
« Reply #44 on: July 17, 2010, 01:31:25 PM »
Hehehe awesome. a lot of work for a pile of iron dust... but cool. I've been following this thread wiith a lot of interest, thinking about doing my own radial.  (I have quit e a bit of experience with epoxies, but no milling/lathe stuf) , so typically most of the stuff I fab is glass/kevlar/fiber  under vacuum when I can. Guess that is what peaked my curiosity on you project.

Rover, I think there's more than one way to skin a cat here on how to build a core.  If you could build a decent mold a stator core could be cast that comes out of the mold perfect, requiring no machining whatsoever other than a little work with a file to clean up some rough edges.  I went for rather a crude method - a bottom cut off a 5 gallon pail with a piece of PVC pipe stuck in the middle.  The PVC wasn't the right OD (it was 6"), which required cutting better than 1.5" out of the inside of the ring on the lathe.  Plus I didn't cut the 5 gallon pail off very straight so part of the ring ended up 2.2" thick and some of it was only 2" thick.  That required facing it on the lathe to make it the same thickness all the way around.

But if you're really good at making molds (I'm not) there's no reason one of these things couldn't come out perfect with no machining required.

This is the first mold I built.  Now this thing is a work of art - a chunk of big channel I found and torched off, a rolled 2" x 1/8" steel ring welded to it, and four nuts tacked in the center to pilot the PVC ring on.  I didn't use this mold.  In retrospect I should have because I would've gotten a lot more accurate ring out of this one than using the bottom off a 5 gallon pail.


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« Last Edit: July 17, 2010, 01:53:14 PM by ChrisOlson »

Darren73

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Re: Radial Flux Generator Project
« Reply #45 on: July 17, 2010, 02:07:20 PM »
Chris,
Nice work, wish I had the time and facilities to tackle something similar, individually rectified verses star or delta will return more power as the star wastes power through the coils and delta is prone to circulating currents which do not exist in the IRP option. As you only have 3 cores buried depending on ratings and practicality you could rectify at the tower base and only use 2 of the buried cores for power. braking can be achieved if needed using a contactor and the 3rd core to drive the contactor.

I can provide more details on the contactor option if it's of interest.

Regards

Darren

Rover

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Re: Radial Flux Generator Project
« Reply #46 on: July 17, 2010, 02:41:30 PM »
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But if you're really good at making molds (I'm not) there's no reason one of these things couldn't come out perfect with no machining required.

Kinda what I was thinking ... Nice piece of work, but with some small alterations a  brake drum from a junk yard ( truck maybe) ... would do as a mold... (instead of going in to out .. would mean going out to in )

probably over a 1000 ways to skin a Cat..  :D


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ChrisOlson

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Re: Radial Flux Generator Project
« Reply #47 on: July 17, 2010, 02:47:12 PM »
As you only have 3 cores buried depending on ratings and practicality you could rectify at the tower base and only use 2 of the buried cores for power. braking can be achieved if needed using a

That would also certainly be an option, Darren.

However, I just unwound my test coil and measured the total length of wire used in one coil so I could figure the average length per turn.  The killer is the length of the winding heads with a 12/18.  Star comes out on top in this one based on the fact I can stuff AWG 13 wire in the holes and only needing ~23-25 turns per coil.  The internal resistance should come in around .49 ohm, which is pretty respectable for a 24 volt 2 kW gen.

 AWG 13 will easily handle 2 kW spikes and 1.5 kW sustained with good cooling on a 24 volt in star.  So I think that's the way I'm going to go with ii.  You can't get too hung up on winding configurations - you have to go with what will provide the least resistance from the generator to the batteries, and in this case star wins.  You can always add resistance someplace to fix a stalled turbine.  But it's hard to remove resistance if you build it in.
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ChrisOlson

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Re: Radial Flux Generator Project
« Reply #48 on: July 17, 2010, 02:56:06 PM »
Kinda what I was thinking ... Nice piece of work, but with some small alterations a  brake drum from a junk yard ( truck maybe) ... would do as a mold... (instead of going in to out .. would mean going out to in )

Well, there's some advantages with using an internal rotor - cooling is the main one.  If you wind a bunch of coils on an old tractor flywheel and stuff it inside a brake drum with magnets, how are you going to get air thru it?

Air will flow freely thru this generator and around the exposed coils as it flows thru.  This thing is going to have a shroud on it with a 8 blade ducted axial fan in the rear that pulls cooling air thru it from the front and exhausts it out the rear.  It's kind of like your car alternator.  If you made a mold, put your car alternator in it, cast it in a chunk of fiberglass resin and bolted it back on the car, how long do you think your alternator would last or what kind of duty cycle would it have?
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Re: Radial Flux Generator Project
« Reply #49 on: July 17, 2010, 03:26:30 PM »
So basically your just making a large motor conversion type genny, "with a fan" to help cooling. I thought the big ordeal was all about using the delta connection? Nothing hard to understand yet. its fun watching you work anyway. Might try just rewinding a motor conversion to reach your output goals? You could add a smaller gauge wire set of coils to help low wind output and a larger dia wire for high wind/rpm output? Im just thinking of the simplicity of it all. Im not a complicated thinker.

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jimovonz

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Re: Radial Flux Generator Project
« Reply #50 on: July 17, 2010, 03:49:35 PM »
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Flux flows or moves better thru iron than open air from the north pole to the south pole.  With the horseshoe magnet the flux is traveling from pole to pole thru the open air and it wouldn't pick up the nail at a distance of 1.5".  Iron can direct magnetic flux, and the test with the nail told me that the iron is directing the flux thru the core from the north pole to the south pole so the lines of flux can be cut by the coil windings as the rotor rotates.  If the magnetic circuit thru the core was open it wouldn't work.

I suppose this might be a positive result if you had one leg of the horseshoe magnet against the inside of the ring and the other was positioned somewhere outside it (I don't know how big our horseshoe magnet is). In this case the flux would be forced to travel outside the ring to return the other pole in any case and would quite likely prefer to travel via the iron nail. However, if you were placing both poles of the magnet on the inside I still contend that the nail on the outside should not be affected. Here I have run a FEMM analysis on the 'CoggingTorque' example which models the laminations in a PM motor. I have expanded the scope of the analysis to include the airspace around the outside of the laminations and added an iron rod to simulate the nail. I have removed two of the magnets so that only the two that represent the poles on the horseshoe are left.



Notice how no flux travels outside the ring. The flux in the nail in this simulation measured around 0.0015T.
For any significant amount of flux to effect the nail, it would have to represent a 'path of least resistance' and since it is obviously a less direct path than straight through the ring alone, you would have to surmise that the ring was saturated.

Quote
The test with the paperclip on the back of an axial rotor serves a different purpose.  There you're using steel plates to direct flux thru the air gap and you don't want flux on the back side of your plates where there's no coil windings.

Isn't this exactly what we are doing here as well? We are checking to see if all of the flux is contained in the structure we have specifically provided to channel it. The fact that the ring improved your magnets 'nail wobbling ability' still fits my explaination. Magnetic 'resistance' of a circuit past saturation is equivalent to that of air, but up to that point you still get an improvement and so an overall net advantage is still possible which is why your nail wobbled.

ChrisOlson

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Re: Radial Flux Generator Project
« Reply #51 on: July 17, 2010, 03:53:48 PM »
So basically your just making a large motor conversion type genny, "with a fan" to help cooling. I thought the big ordeal was all about using the delta connection? Nothing hard to understand yet. its fun watching you work anyway. Might try just rewinding a motor conversion to reach your output goals?

Electric motor conversions are too heavy, you have to build a rotor for it anyway, and the output ends up being not all that great for the size and weight.  This thing should come in under 25 lbs ready to bolt on the turbine.  It could be build standalone with it's own bearings in it for PTO drive in a nacelle based turbine, or it can be mounted directly on the shaft on a mainshaft style turbine, either behind the prop hub or on the back similar to my latest rear-gen unit.

I don't think this design could be well adapted to a trailer spindle style turbine because things aren't accurate enough there to keep the rotor from hitting the stator.  Excessive play in those tapered roller bearings and the generator would be junk, which is probably why ball bearings are primarily used in generators and electric motors.

So there's pros and cons.  If you're into converting old electric motors that's good.  If you want to roll your own and get decent output with less weight, this is for those folks.

As far as the winding, like I said, it all depends on the layout.  For maximum performance vs simplicity it appears to me that star is the way to go on this one.  I could get better performance from it with a 12/36 layout and delta winding.  But the build then becomes complex beyond what most people can do.

So far I have built this thing with only the use of normal shop hand tools, a digital caliper and a lathe where it can be done on a small one with less than 8" swing.  No mill with a rotatory table required, no CNC cut or machined parts, all simple stuff.  If you have those tools, it will be a lot easier.  But, for instance, I cut the teeth in the stator core by marking it out with a marker and digital caliper, and a hand drill and hacksaw with the ring clamped in the vice.  I got a mill with a rotary table on it but I did it the difficult way just to make sure it can be done.  It's like Hugh has pointed out with his designs - if you build a piece of engineering excellence but nobody can duplicate it, then the average homebuilder gains nothing.
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ChrisOlson

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Re: Radial Flux Generator Project
« Reply #52 on: July 17, 2010, 04:00:40 PM »
Isn't this exactly what we are doing here as well? We are checking to see if all of the flux is contained in the structure we have specifically provided to channel it.

Well, like I said before, I don't really know and this is entirely all possible.  If this core ring doesn't work I'll figure out how to build another one that does, and still be easy to construct.  I only have about $11 in fiberglass resin invested in it, a bunch of free iron powder, and some time and fun in building it.  If it don't work, I'll study up on why, and fix it    :)
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fabricator

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Re: Radial Flux Generator Project
« Reply #53 on: July 17, 2010, 04:51:18 PM »
OK, so if a guy has easy access to a laser table and a high def plasma table, what would be the best steel to cut laminations for a core like this out of? Good old black iron or cold rolled or what? The next question is what is better, a lot of laminations out of 18ga or less out of 7ga?
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ChrisOlson

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Re: Radial Flux Generator Project
« Reply #54 on: July 17, 2010, 05:50:53 PM »
OK, so if a guy has easy access to a laser table and a high def plasma table, what would be the best steel to cut laminations for a core like this out of? Good old black iron or cold rolled or what? The next question is what is better, a lot of laminations out of 18ga or less out of 7ga?

There's low loss electrical steel sheet you can get to make those laminations out of.  That's assuming you want to shell out the bux for it.

This core I built is supposed to be a compromise.  Low losses due the iron particles being insulated from one another to prevent eddy currents, with lower magnetic efficiency as compared to laminated steel cores.  When the magnets get here sometime next week I'll find out how well it works.
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joestue

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Re: Radial Flux Generator Project
« Reply #55 on: July 17, 2010, 08:31:31 PM »
Powdered iron cores have no problem handling the same flux densities as do laminated steels.
The issue is that it takes 50-1000 times the ampere turns to get there, and the particles don't have the advantage of being "grain oriented"
So, *normally* they find themselves in chokes and filters (3-30Khz, and .5 or less teslas)
once you need to get higher energy densities than this you make the jump to 20Khz to 100Mhz ferrites,

I have a 500 watt varac that weighs 5 pounds, and consumes 6 watts idle. estimated flux density is around 1T.
if you want to make an axial iron cored machine, it is rather easy to get the electrical steel in the form of a steel strip, and you can also recover this from most toroidal transformers. but getting custom cores punched out is going to be expensive, as you will have to pay for the tooling.
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fabricator

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Re: Radial Flux Generator Project
« Reply #56 on: July 17, 2010, 09:20:14 PM »
Custom cores can be cut on a laser with no special tooling, high def plasma will do the same thing just not quite as accurate.
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ChrisOlson

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Re: Radial Flux Generator Project
« Reply #57 on: July 17, 2010, 09:28:53 PM »
if you want to make an axial iron cored machine, it is rather easy to get the electrical steel in the form of a steel strip, and you can also recover this from most toroidal transformers. but getting custom cores punched out is going to be expensive, as you will have to pay for the tooling.

Ed Lenz built both:
http://www.windstuffnow.com/main/poured_stator.htm
http://www.windstuffnow.com/main/alt_from_scratch.htm

He got slightly less efficiency with the powdered iron core as compared to the laminated steel but felt the tradeoff in construction difficulty was acceptable for slightly less magnetic efficiency.  I don't recall what Ed used for magnets but I think he tried both ceramics and neos with it.  It ended up being a little 8" diameter 650 watt unit with 8 foot blades on it.

I ordered N42 neos for this one.  When I get a stator mount built, get everything assembled to a turbine shaft and can spin real magnets in it I'll have a better idea of what sort of magnetic efficiency I get.
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joestue

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Re: Radial Flux Generator Project
« Reply #58 on: July 17, 2010, 09:42:07 PM »
His steel strip unit wasn't really doing much but negating the need for another set of magnets on the other side, you still have the flux leakage, and you have to supply the necessary H to push 1T or whatever through the air gap. not to mention the fact that you aren't reducing any eddy current (possibly negligible assuming a single coil)

what i'm taking about is drilling the holes and slots out as you did, but axially as you would do with steel strip and an air gap on the order of .05 inches or so.
This requires a dual sided rotor, as the magnetic attraction is in the tens of pounds per square inch.

My interest in this is ferrite cores for 50Krm turbine engines, so most of the stuff i do isn't really applicable, but the math still works provided you do it.
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Re: Radial Flux Generator Project
« Reply #59 on: July 18, 2010, 10:04:16 AM »
Thinking about your cooling by "design". In order for a fan to draw air through the generator it will need large entrance holes. What will your entrance holes do about the rain, dust and ice formation? Cranking out 2kw and soaking wet coils may not be a real good idea. Although it may be impressive for a second watching the smoke. You say you like using JB weld, but do you realize JB weld crawls up the magnet when applied? Im not sure a void under the magnet will keep JB weld in place without it crawling around and opening that void back up. I dont know, Ive never wanted to attempt it. Lastly, you may want to rethink your 5 thousandths air gap. Not only vibration of the coils causing a rub but even gluing the mags on I doubt will keep your rotor within 5 thousandths of an inch. Ive always been told to keep the air gap at half the magnets thickness or slightly less. Amazing how similar a garbage disposal stator looks compared to your home made.

This comment ended up in the wrong thread so I tried my copy and paste skills to see if I could move it here.

The coils are going to be sealed with air-dry electric motor varnish when I get the stator done to fill voids in the winding and prevent coil vibration.  I'm pretty good friends with a local fellow here who has an electric motor shop and he said he'll varnish it for me just like they do electric motors.  Initial testing will be done, however, without varnish in case I have to unwind it and rewind it in case I don't get it right the first time.

Alternators on tractors and offroad equipment run in much more severe duty conditions than a wind turbine, with dust, water, dirt, etc.. with open coils and fan cooling with not a single problem.  A lot of this equipment gets pressure washed to clean it up with the pressure washer blowing water directly into an open alternator with slip rings - and they still work without a hitch.  This one will too.

Secondly, the air gap is not adjustable in this type of generator so there's little room for error in winding.

I have run the magnet to stator gap at the thickness of a piece of paper on axials with JB Welded magnets in the past with not a single problem pushing 1.5 kW.  It does not rely simply on the JB Weld.  The magnets are also pinned.  The mags come with 1/8" holes and I use 1/8" split pins.  They have to pressed in place over the pins because it's an interference fit.  The force to remove the magnet from the pin is greater than what the magnet has for attraction force to the steel rotor.  To do the initial fit of the rotor to the stator I made "dummy mags" out of 1" x .5" bar stock.  The other day when I was doing some figuring on forces and what I need to hold those mags on there I spun my rotor in the lathe at 600 rpm with the dummy mags on - no magnet attraction, no glue - just the pins holding them.  They didn't even attempt to move at 600 rpm with just the split pins holding them in place.  The JB Weld is secondary.

I'm starting out with a .005" air gap between the magnet face and stator core until I find out how much flux I'm going to get thru the coil legs with N42 magnets.  That will be done by winding a test coil with the number of turns based on my experience building dual rotor axials, based on a .750" air gap.  When I find out how close this thing comes to that benchmark, then I will adjust the final air gap by removing the core, unwinding the test coil, and machining the inside of the core, if necessary, to increase it.  I have no problem machining and building things to +/- .0015" tolerances - I do it all the time.  It's easy to add air gap if the initial tests show it can be increased.  It's not so easy to decrease it if it's built too wide to begin with.  If I end up with a .050" air gap in the end, that's even better.

If anybody else has ever built one of these from scratch then I'd have something to go by.  But all I've seen is crude stuff like sticking coils inside brake drums and such, and certainly nothing with an internal rotor with a homemade powdered iron core that I've ever seen in the homebuilt stuff.  So there's a lot of unkowns and I prefer to build a cushion into it for initial testing to cover the unknowns.

It seems there's a lot of people interested in this generator design, based on the emails I've gotten on it.  Like one fellow said, he's glad I'm going thru the "labor pains" to build it because then other people have something to go by if they want to attempt it.  Until then I'm breaking new ground, and when you break new ground you never plow it too deep the first time over.
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Chris

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Re: Radial Flux Generator Project
« Reply #60 on: July 18, 2010, 11:42:29 AM »
I've done my share of motor conversions. Your gap is adjustable with the rotor diameter. A 5 gallon bucket sized motor conversion or a home made radial is not breaking new ground. Its just increasing the over all size and "possible" output by allowing you to wrap the coils with a wire gauge that suits your needs. Motor conversions, your kinda stuck with what you get unless you re wind the coils.

Only difference I see is the stator core materials. I thought using Delta wiring was breaking new ground? Now that that was discussed over a week, I read your back to Star connection. Hint* motor conversions usually are connected star or jerry.

On the car alternator comparison, car alts are not out in the weather nor do they suck air, rain through the front and blow it out the back. Quite the opposite.

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clintonbriley

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Re: Radial Flux Generator Project
« Reply #61 on: July 18, 2010, 12:45:17 PM »
Quote
Electric motor conversions are too heavy, you have to build a rotor for it anyway, and the output ends up being not all that great for the size and weight.  This thing should come in under 25 lbs ready to bolt on the turbine.

Great thread, I look forward to seeing how the experimental radial generator works out. 
I'd like to better understand why it is that a motor conversion's output is so low for its overall weight
even when the coils are rewound for a specific rpm range. 
Rotor diameter too small?
Excessive steel in the stator?
Too little room for wire in the slots?
What effect does the length of the rotor and stator assy have?
Yours is quite short compared to a typical motor.
I'm guessing you'd need to go with a large dia rotor to get better
low rpm generating capacity like is done with the axial types, right?

Clint

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Re: Radial Flux Generator Project
« Reply #62 on: July 18, 2010, 12:56:50 PM »
From what Ive learned, its getting the most magnet on the rotor possible for decent output on a motor conversion. Increase the poles, magnets and rotor diameter and I cant see how it would not make more power than a smaller motor conversion. A small axial = low output, larger axial= more output.


Im just a newbie with a few years of hands on practice.


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ChrisOlson

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Re: Radial Flux Generator Project
« Reply #63 on: July 18, 2010, 02:32:06 PM »
Only difference I see is the stator core materials. I thought using Delta wiring was breaking new ground? Now that that was discussed over a week, I read your back to Star connection. Hint* motor conversions usually are connected star or jerry.

On the car alternator comparison, car alts are not out in the weather nor do they suck air, rain through the front and blow it out the back. Quite the opposite.


As far as the delta winding, like I said before, it won't work in this one.  I'd have to go to either 6/18 or 12/36 to make that work.  I decided to stick with the 12/18 because of ease of construction and winding.  I talked with Ed Lenz briefly about this, and there's not even a doubt I'd get better performance from a 12/36 delta vs a 12/18 star.  This one is going to be 12/18 star to get the bugs out.  You can rest assured that build #2 will be a 12/36 delta.

Back to cooling, you have a misconception if you think water can get in anything in this unit and cause smoke.  If that happens there's a shorted stator coil someplace and the stator needs to be pulled and rewound anyway.  And I didn't say anything about a car alternator, which is a light, intermittent duty unit (car alternators are not designed to put out their peak output continuously).  I was talking about alternators in offroad and construction equipment that run right out in the open in some of the most severe duty conditions on earth.  They are invariably air cooled by moving air, with contaminants, thru them from end to end.  It doesn't make a lick of difference which way the air flows thru the unit, or whether it's sucked or blowed.

I've worked around that kind of equipment virtually all my life and stator failures are almost non-existent in those units unless a bearing goes and the rotor hits it.  I've seen them so packed full of dirt that you get a full pound of dirt out of a big Bosch 135 amp 24 volt by blowing it out with an air nozzle after a week working in dust so thick a human can't breathe it - and they still don't fail.  Rotor failures are far more common due to slip ring failure from abrasives carried in the cooling air.  Internal regulator and diode trio failures are even more common yet due to their inability to deal with the heat and vibration.  This unit will have none of that stuff in it - no slip rings, no internal regulator, no diode trio.  Just a heavy-duty forced-air cooled stator and a rotor with magnets.  It could suck a water-soaked Canadian goose into it and it's not going to hurt it unless a drumstick gets caught between the rotor and a stator tooth and locks it up.  In that case, lower the tower, rinse it out with a garden hose, retrieve any pieces of meat that be thrown on the grille, and she'll be good to go.

To put this cooling issue in perspective, many utility-scale turbines have forced-air cooling on the generator.  They use one helluva big fan that sucks air in thru forward air intakes, sucks it thru the generator, and exhausts it out the back of the nacelle.  This unit that I'm building was not conceived in a wild nightmare one night.
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Chris

DanB

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Re: Radial Flux Generator Project
« Reply #64 on: July 18, 2010, 04:52:46 PM »
Quote
I've worked around that kind of equipment virtually all my life and stator failures are almost non-existent in those units unless a bearing goes and the rotor hits it.  I've seen them so packed full of dirt that you get a full pound of dirt out of a big Bosch 135 amp 24 volt by blowing it out with an air nozzle after a week working in dust so thick a human can't breathe it - and they still don't fail.  Rotor failures are far more common due to slip ring failure from abrasives carried in the cooling air.

It does depend.  On small wind turbines with radial flux alternators stator failures are still not uncommon... because they are pushed hard and don't enjoy the predicatable life that most motors/generators do.  I've heard of many stator failures on Bergey wind turbines, ARE...  etc.  Seems like everyone in small wind power is struggling with similar problems really.    Most of these machines do have one difference from yours though, that is that the magnets run outside of the stator (not inside it)... which, has lots of advantages but cooling is probably not one of them.  I expect yours may shed heat better having the stator on the outside like a more conventional motor.

Can't wait to see how it works...  at the rate you seem to get things done I expect we won't have to wait long for a bench test anyhow!
If I ever figure out what's in the box then maybe I can think outside of it.

ChrisOlson

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Re: Radial Flux Generator Project
« Reply #65 on: July 18, 2010, 05:07:20 PM »
Can't wait to see how it works...  at the rate you seem to get things done I expect we won't have to wait long for a bench test anyhow!

Well, right now I'm building a conflagration to mount it to a turbine head using my existing stator supports.  The stator support for the axial is a lot bigger than the radial so I have to make a special mount for it.

The magnets won't be here until sometime the middle of this week.  So once I get it mounted to the turbine head I'm kind of dead in the water until I get those mags.

This is one of the funnest generators I've ever built because it requires thinking outside that box without knowing what's in it   :)

edit: Dan, on this issue of failures, I had a little Chinese built turbine once with 1 meter plastic blades on it.  I can't remember the brand of it but it was supposed to be 300 watts.  It never did put out 300 watts - 100 in really good wind.  I had it for about a year and it locked up one day and punched a hole in the generator case.  I took it apart and it had little arc magnets super-glued to a steel rotor and one of those magnets had come off.  The windings in it weren't any heavier than like 22 gauge and it was very poorly wound with wires crossing over the stack - just a messy job of construction.  I still got that thing around here someplace.  I think it's on top of my office in the shop.  If I get time at some point I'll pull it out and take some pictures of it so people can see what's in it.  It was a little radial generator with laminated core.
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« Last Edit: July 18, 2010, 05:29:28 PM by ChrisOlson »