Magnets for conversion

[offshore79]

I've wound my first stator but could use some clarity on my rotor. I've experimented with ceramic magnets and read over allot of the posts including "coils, coils, coils" which seems to offer allot but I need one step further.

First the stator:

I had a generator available to me so decided to convert it for wind use.

It has a 4.45 ID (8" OD) with 36 slots. I rewound it with 2-#19 wires with 20 turns each coil. This is a lap wound stator so 2 coils share a slot with each leg of one coil in every other slot. (The last or first 2 coils were a bear)

The rotor:

Originally this was going to be a brush type but I had some manufacturing limitations and from all that I read the magnets sound like the better choice anyway.

I'm looking at 12 N42 magnets but I'm torn between 3"x .75"x.5" and 3" x .5" x .25".

In either case there would be a less than ideal alignment between the magnets and the coils but it would be close either way.

So my question is, would there be any magnetic cancellation with the bigger magnets that would make the smaller magnet the better choice? Or would it be better going with the larger magnet with some magnet to coil overlap?

I hope I've given enough info.

Also, with the lack of experience with the N42 magnets, any stabs at what kind of power I could expect to see with this set up?

I'm leaning toward VAWT and thinking 4 ft dia x 4 ft high. And a 2:1 or 3:1 gearing.

Thanks

[offshore79]

http://www.otherpower.com/images/scimages/11806/wind_gen.jpg

This is a dwg of what I have.

[Airstream]

I think your cogging is going to be severe - in a tight airgap laminate cage perhaps less is more?

Also it's "wise and smart to invest in..." long bar magnets and not try to patch two or three smaller pieces into a 3-inch magnet. I had to affix two one-inch magnets onto a two-inch iron backer plate and although I did eventually get the two mags to sit alongside each other it took several days time and many trials to get something that would work - and then the epoxy fails and the mag flips around and crashed into the air gap and ruined the other mags too for my all my effort.

[Airstream]

Ahh - you posted a drawing while I typed - I'd be looking for quarter-inch width to match the slot width - and unless this is a non-wind powered alternator that has enough tourqe to break zero speed iron seeking lock up you might get away with small button magnets instead of bar to keep the cog down to a minimum...

[offshore79]

Well,

Thank you for all the good feedback.

I'm going to go with the thinner magnets. N42.

They are the thinnest I can get and still span the stack/rotor length.

3" bar it is.

So, another question.

I get around 1.5 -1.6 VAC from a ceramic magnet from a coil on my test stand (1200 rpm or so), what could I expect to get from the Neo magnet in comparison? (I could just wait but I'm impatient)

Just a guess from someone that has compared the two would do.

Thank you all again.

[offshore79]

After looking over "coils, coils, coils" again, should I be using 24 magnets? They would be touching all the way around but it looks like they would fit and be in phase.

 http://www.otherpower.com/images/scimages/11806/wind_gen.jpg

Thank you

[Airstream]

If it is for wind I think you should be looking into non-bar shaped magnets.

Having a row of six or eight button magnets skewed, not inline with slot laminates, reduces rotor cog of zero rpm iron attraction from all those bar magnets...  ...12 x 3" = three feet of neo pull across a tight airgap equals the turbine won't move until some serious wind occurs!

Skewing also can mean allowing the degree interval of magnet separation on the rotor drift fractionally so as few magnets as possible will align to true center of any laminate slot walls at any one time.

There have been some very good write-ups on conversion rotor style. Google is your friend!

[signweld]

You mention "coils, coils, coils"

is this a story or comment? I searched for it and come up empty.

[offshore79]

http://www.fieldlines.com/story/2008/10/7/124436/787

This is close to the post coil coils coils but I have to admit, I cant find it now either.

It may be the old fashions tonight but who knows.

[offshore79]

Found it.

http://www.fieldlines.com/story/2004/1/11/0022/78182

[offshore79]

Well, you were so right on the cogging.

Two fingers is not an option.

I used some steel armature lams that had an equal 36 tooth configuration. The OD of the armature lam is slightly smaller than the original rotor so I figured between that and once I cut out every third tooth, slid a magnets in that there would actually be a bit more of an air gap then I had in my drawing. I figure about a .125 air gap and unfortunately skewing was not and option.  Well, not enough of an air gap to overcome the N42 bar magnets. Cogg monster!

I have to grip it with my full hand. I had planned on needing to gear it up to generate the voltage and amperage I want but I will now have to gear it down to get it to turn more easily.

This should still work out ok. I did a one coil test with a drill and with the drill on it's lowest setting, just enough to start spinning (I guess about 50 to 80 RPM) I had .8-1.0 VAC.

At 36 coils that would be above cut in on my 24v battery bank. If I can gear it to say .5:1 or .75:1 I may be able to get my cut in at a reasonable wind speed.

However once this thing is spinning it looks that it can put out some serious power. At 1200 rpm (just out of curiosity) It was around 10VAC+ for the one coil.

WOW. I cant wait to find out what the amperage will be.

I will be adding photos of the rotor and stator soon.