Zubbly's 25 hp baldor

[monte350c]

This first comment is a test to see how the pictures look.

It's the geometry for a 25 hp Baldor with 1" x .5" x 2" mags on the rotor.

Zubbly, I took a look at the picture you posted of this machine before, and took a guess at a couple of numbers. I put the OD of the lamination stack at 11.56", the length of a slot at 1.25" and the slot width at around .25". Hope that's close!

I didn't take the flat parts on the stator OD into consideration.

This simulation is 1" deep if you can imagine it goes to that depth into the page.

The magnets are N37 since the program didn't have N35.

The airgap (ie between the corners of the magnet and the stator) is .040".

If this works as planned, you will be able to click on a picture to see it full size.

We'll see!

Anyhow, the pic above is with the magnets sitting flat on the rotor, something like Jacques did for his 215 conversion.

The next pic is the flux. The point in the output box sitting at 1.6T is in the purple section on one of the stator teeth.

The normal flux plot in the airgap over 2 poles:

The integral over 1 pole for the flat mags is .8046T

Next for the 1" round magnets. The surface area of a 1" round magnet is about .785 square inches, so I for the simulation I used the .785" for the width and left the simulation depth at 1". I believe this will come close to the effect of using round vs. rectangular mags.

The geometry for the round setup assumes flat spots have been milled into the rotor for the mags to sit on.

The flux density plot:

The normal flux in the airgap over 2 poles:

The integral over 1 pole is .6684T

So all things being equal I would choose the flat magnets (1 x 2 x .5) over the round ones!

If you download a copy of the FEMM program let me know and I'll post the files for this - that way you can open them and play with this on your own PC.

Ted.

[monte350c]

Sorry about the pic size - I have fixed the files so they're not so large.

Ted.

[zubbly]

Hey Ted!

It looks cool!  

Recently did a conversion using the rectangular mags (didn't like working with them)

Will probably end up using the round because of the way i make the mag cages.

Thanks for all your effort

zubbly

[monte350c]

Hi Zubbly,

No problem!

Actually that was kinda neat - it's the first run I've done of a 48 slot stator.

I thought of leaving a small ridge of maybe 15 or 20 thou on the edges of the flats where the rectangular mags would sit - to stop them from moving sideways. Then run a piece of wire lengthwise down the magnets, tensioned at the ends of the rotor to hold the mags on. Or some kind of clip - there is a bit of room in the centre of the magnet where it's furthest from the stator.

Still the flux in the airgap is significantly better for the rectangular mags - .8046T or 8,046 gauss vs. .6684T or 6,684 gauss for the round ones. That should translate into about 20% better performance for the 2 x 1 x .5" mags.

However that might be overshadowed by ease of construction - it's always a compromise in some way or another!

In any case this conversion should be a real performer.

I am beginning to think it's a great idea to put very big blades on an alternator - to take best advantage of the lower winds. Then use a furling system that allows continued but reduced operation in higher winds. ie. not an all or nothing furling plan. The gravity tail thing seems to fit that quite well.

I have to get some blades made for my 1.5 hp conversion and see what that will do.

Ted.

[Garry]

I think I posted this a long time ago but maybe it's worth a repost. I wound the rotor on a ceramic conversion with fiberglass filament that I bought surplus. About $1.00 worth did the trick and only added about .010 to the radius. Just run the filament through an epoxy bath while spinning the rotor on the lathe at slow speed. When you get the rotor covered let the lathe run until the epoxy is hard. The result is stronger than a band of steel of the same thickness and non-magnetic.

Garry

[drdongle]

Where do you get fiber glass filliment?

[Garry]

I bought mine at C&H sales company 800-325-9465

I don't see it in their current catalog but they may have small quantities. Mine was ten pound spools for four dollars.

Garry

[Garry]

This material is available on their web site.  FIBERGLASS YARN OWENS CORNING, #G37-1/3 2.8S. Continuous filament fiberglass yarn. Has breaking strength of 10 to 12 lbs. Approx. size 1/64" dia., white, splice-free. Supplied on plastic conical spindle. Suited for lacing or wrapping cables used at high temperatures, etc., or for any high temperature wrapping application. Size:13-1/2" high x 6" dia. at base and 1-5/8" dia. at top. Weight of yarn approx. 3 lbs. Stock #MI8100 $4.00

Garry

[ghurd]

Could it be wrapped on, then epoxied?  Maybe a paint brush?

I know I'm too lazy to figure out an epoxy bath with what I have available.

G-