Author Topic: 9 coil / 6 magnet PMA from left over parts (Read 5638 times)

elt · « **on:** July 18, 2007, 06:20:51 PM »

I did this backwards from normal - I made the stator and ran some "test magnets" on it... To get what test data I could, I cobbled together some rotors from ceramic magnets I had on hand and am now wondering if my test data gives any help or at least a guess as to what kind of neo's to use with it.

I had some left over wire and resin from my 10' mill so I built the stator that I asked about in this post...

http://www.fieldlines.com/story/2007/1/17/23030/2076

I had enough wire for 9 coils of #15 wire with 40 turns each.

Here's a picture of the stator ready to pour...

http://www.otherpower.com/images/scimages/6527/96_stator_02.jpg

The holes in the coils are 1"x2"; the resistance across two legs in star configuration is .6 ohms.

I cobbled some rotors together to test it. I only have some ceramic magnets right now, each rotor has six. They are .9" x 1.8" x .35". I estimate they have a max pull of about 1 to 1.5 pounds. Here's the bottom rotor made of two 8" saw blades.

The top rotor has 6 more ceramic magnets on a single 10" blade.

The magnets definitely link through the 1/2" thick stator; even before I put the top nut on, the top rotor would turn the bottom rotor as fast I could turn the shaft. (And the back of the blades don't seem magnetic so I think I'm getting about as good a flux path as could be had with these little magnets...)

--%--

Basically:

x 1"x2"x3/8" ceramic magnets, 1.5 pounds of pull
coils of 40 turns of #15 wire, 1/2" thick stator

.6 ohms across two legs in star configuration

air gap, about 3/32"

With this setup I'm getting about 1 volt peak to peak (.6 to .7 volts rms) at 120 rpm. Any way to tell (or swag) what I'd get with neos?

For real magnets (that won't break the bank,) I was thinking either

x 1.5"x.75"x.25" neos , six on each rotor or
x 2"x1"x.5" neos, six on one rotor with an blank rotor opposite to help complete the flux path.

Thank you,

- Ed.

electrondady1 · « **Reply #1 on:** July 18, 2007, 10:01:23 PM »

of course neos will give you more .

but then you will need better rotors.

are you trying to get a usable voltage with what you have?

Flux · « **Reply #2 on:** July 19, 2007, 12:37:33 AM »

I can't follow the logic of what you are trying to do.

Almost any combination of magnets and coils will produce something but you seem to have a muddled idea that is likely to lead to very indifferent results. You may get about a threefold improvement with neo but the whole magnet/ coil arrangement is poor.

Using 6 magnets with 9 coils requires a totally different approach to be much use.Windstuff Ed shows how to do this properly on his site.

I can't help feeling that you would have done better if you had kept a conventional 9 coil arrangement as intended for 12 magnets and just left half the magnets out ( making it unipolar with all N on one disc and all S on the other).

Flux

elt · « **Reply #3 on:** July 19, 2007, 04:59:21 AM »

The only thing there that I intend to eventually use is the stator. I was wondering if anything could be inferred about the possible results with neos from the tests with the weaker ceramic magnets.

What am I trying to do? One of the disappointing things about my 10 foot mill is how heavy it is... I can barely manage to move it around. I want to explore making a compact and lighter alternator. As for the coil arrangement, my hope was that one magnet (or set of magnets) would energize two coils at once... I don't know if it works like that or not. I did look ad Ed Windstuff's arrangement but I think that would result in a larger and heavier alternator not a smaller and lighter one.

Getting "the most" out of my wire isn't my goal. I'm hopping for "pretty good" in a overall smaller size.

I'm not so much worried about voltage. I can make a voltage booster if necessary (thank you!) I am wondering what kind of power might be extracted from this stator and what size blade might be used. (I'm not expecting a "large" blade. With that I can then figure out the mechanicals: what I need for rotor plate, shafts, bearings and hubs.

Thank you,

- Ed.

Flux · « **Reply #4 on:** July 19, 2007, 07:02:47 AM »

"The only thing there that I intend to eventually use is the stator. I was wondering if anything could be inferred about the possible results with neos from the tests with the weaker ceramic magnets."

I really think that what you have done with that stator makes it a very doubtfully starting point for anything. As I said I would expect about a threefold improvement in voltage and in theory about ninefold improvement in power with suitably applied neo.

"Getting "the most" out of my wire isn't my goal. I'm hopping for "pretty good" in a overall smaller size."

That is a misconception, if you want to make a light and compact alternator you need the highest possible efficiency and that means the best possible use of copper ( and magnets). You will not do that unless you adopt a slotted iron core design. Your dream will come at a price of low wind performance.

"I'm not so much worried about voltage. I can make a voltage booster if necessary (thank you!)"

That doesn't make sense either, you can get any voltage you want by altering the turns.

A booster will actually cost you as it will not be 100% efficient. None of this will alter the actual POWER produced, that ultimately will depend on the volts/rpm and the winding resistance.

This thing is so far off any conventional design that I really can't offer you much idea of what it will produce but I would think that with a good choice of neo magnets and decent steel discs you may manage a 6ft prop with that stator the way you are going at it.

Good luck

Flux

finnsawyer · « **Reply #5 on:** July 19, 2007, 08:34:12 AM »

If you haven't already poured the stator and glued down the magnets, you might check out the following:

http://www.fieldlines.com/story/2006/4/21/16237/9933

I don't see much point in what you are doing, either. Why go smaller, when you have the perfect opportunity to try something different and perhaps compare its output with what you did before, especially when you have the magnets and coils left over?

elt · « **Reply #6 on:** July 19, 2007, 10:38:58 AM »

We already did this discussion!

http://www.fieldlines.com/comments/2007/1/17/23030/2076/8#8

Peace,

- Ed.

hiker · « **Reply #7 on:** July 20, 2007, 05:47:45 AM »

if you want a light weight mill..

here you go..about 20 pounds ? good for 200+ watts or more--i chopped the blades ,,

they were longer--didnt need all that power..keeps my motorhome batt. charged all night--with the furnace motor going--cold up here in the winter dont you now..:}

its powered by ceramics with small neoes glued to the top of the ceramic mags..

check out test stand mill in my files --its all made from wood--so far its survide

45-55 winds --and its a few years old--still puttin out the juice,, stator is made from plywood with coil cut outs--its all sealed up with layers of varnich--and paint..

the rotors are sawblades doubled up..works for meeeeeeeeeeeeeee.......

if you want more info drop me a line.......hiker at adnmail dot com

hiker · « **Reply #8 on:** July 20, 2007, 05:54:38 AM »

thougt i had that e mail address hidden --oh well.......

finnsawyer · « **Reply #9 on:** July 20, 2007, 08:15:21 AM »

You expect me to remember every discussion that I ever had on this board? Not likely. In any case, keep in mind that new people come on board and they are not aware of what went on before. Your posting the link may help in that respect, but I have to ask why you are wasting everybody's time by bringing it up again? Why didn't you just build the thing and present the result?

elt · « **Reply #10 on:** July 20, 2007, 08:42:24 AM »

> You expect me to remember every discussion that I ever had on this board?

Of course not. But on the other hand, its pretty obvious that you didn't even read this story before trying to coop me to build your design... just like in the initial discussion which, by the way, was the very first link in the very first post to the entry, where you tried to coop me to build your alternator... I thought that I'd point that out for any new people that may have come to the board and were not aware of what went on before. So to paraphrase you, why don't you just build the thing and present the result. I've tried to be as civil about this as I can be both in this thread and the last: I am not going to build your alternator!

elt · « **Reply #11 on:** July 20, 2007, 04:52:12 PM »

Thanks Flux.

That rotor setup wasn't really doing what I expected... thinking "one magnet energizes two coils" at once, I expected 60 hz at 60 rpm but that didn't happen; in was 60 hz at 120 rpm. I placed the 12 magnets on one rotor

This way, I do get 120 hz at 120 rmp but only about .85 volts. Less than before but I only have magnets on one side. So (no surprise to folks that know, I guess) pound per pound, opposing magnets work best...

What about dollar for dollar? When I go shopping to replace the ceramic magnets, I can get 24 pieces of 1.5" x .75" x .25" (26 pound pull) neos for about the same price as six 2" x 1" x .5" (70 pound pull) neos... which setup would make more power?

(The test alternator is what I had on hand, saw blades and a wheelbarrow wheel hub. I will get real disks for the rotor and am looking at hubs from racing go-karts as we have a track two driveways down the road.)

- Ed.

finnsawyer · « **Reply #12 on:** July 21, 2007, 08:21:14 AM »

I guess I got triped up by Flux's extensive comments. I thought you were looking for some kind of advice. It's your diary. My apology for messing it up. I'll try to remember your handle in the future and be sure not to give you any more advice.

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