Author Topic: New to the Forum (Read 1313 times)

Murlin · « **on:** May 17, 2006, 07:39:58 PM »

Howdy folks. I sure am glad I found this board. I have been wanting to build a wind alternator for quite sometime and happen to stumble onto this site. The info in here is priceless. Hats off to everyone in here.

I am not an electrical engineer, my expertise is in mechanics and CAD/CAM, as I have my own machine shop.

So from time to time I may ask some very stupid questions so bear with me as I am eager to get started on a 10' model.

Since this is my first post, it wouldn't be right not to start off on the right foot by asking my first dumb question.

So here goes.

I have not seen anyone use any steel plates on the sides of the magnets on the rotors. Would this not make the existing magnets stronger? kinda like the machinists mini-mags.

I am sure since I have not seen you guys doing this, there must be a reason.

Thanks for your time.....

Murlin

coldspot · « **Reply #1 on:** May 17, 2006, 03:01:21 PM »

Welcome !!!

To keep the flux field from flowing wrong

the magnets need to not have any way for the flux to easly skip the coils and just

flow around to the other side of themselfs.

As they would with anty metal being that close to them.

So to keep the flux flowing to the other magnet across from it

(thru the copper coils)

Metal should be kept away from the magnets.

Of course you will need metal as a backing to keep the flux

from getting away and instead flowing to the next magnet to themselfs.

just what I've learned here!

lol

DanG · « **Reply #2 on:** May 17, 2006, 03:05:43 PM »

Magnetic flux can't be reflected like light or a stream of water - imagine the densest flux fields as underneath magnet's surface. The lines of force extending beyond the surface want nothing but to loop-the-loop at center of magnet. However the center is so full many lines of force get pushed out through air onto a forced walk-about.

An iron backing on one side gives that sides' force lines a shortcut close to magnet core, enough that it boots / shifts more flux lines out as air walk-about flux lines on the opposite side (where we can find them to get better work out of them)

Any iron alongside the magnet will draw back many air walk-abouts closer to the core - your mini-machinists mags depend on contact to capture the remaining flux lines to keep them densely clustered and holding the work, or working the hold so to speak.

Anyway, anything metal especially ferrous materials on sides of magnets short circuit too many flux lines back to underneath magnet surface where we can't get work out of them.

That was fun - hope it makes sense : )

-

SparWeb · « **Reply #3 on:** May 17, 2006, 04:44:05 PM »

This might help visualize:

Some lines of flux wrap around the edges of the magnet, and back into the backing plate. These lines will not help produce electricity, because the coil won't pass through them. Putting a "cup" around the magnet would make that effect even worse.

Hope that helps.

Murlin · « **Reply #4 on:** May 17, 2006, 04:51:57 PM »

Ahh, so the magnet in the mini-mag didn't actually get stronger, more of the field is redirected so you are using more of it in the area of contact...

So the strength of the magnet is in it's size and the material it is made out of so you can get a denser field to move more electrons through the coil in a single pass of the magnet.....

That makes perfect sense....thanks guys...

This will be alot of fun I can tell already

Murlin teh magnetically challenged...

ghurd · « **Reply #5 on:** May 17, 2006, 05:38:35 PM »

Dang! That has me confused!

But it means (see how the flux lines bend back around at the sides of the magnet) a shorter path to get where it wants to go is bad.

A ferrous material ring will bend more lines of flux away from the stator where it needs to be.

If you want a ring, make it from a non-magnetic material, like stainless or brass.

G-

SparWeb · « **Reply #6 on:** May 17, 2006, 08:43:51 PM »

G, you don't sound confused at all!

WXYZCIENCE · « **Reply #7 on:** May 18, 2006, 10:53:47 AM »

Hello Murlin, let me warn you this board is pretty addictive. Joe

Murlin · « **Reply #8 on:** May 19, 2006, 07:19:05 PM »

I know what you mean Joe. I have been reading every day since I found this site.

OK.....time fow dumb question #2....

I see that you are building 3-phase 48 volt machines that produce quite alot of watts/amps.

If 1 HP takes 746 watts, would it be possible for a 3kw machine to run a 4-hp motor as long as it were operating at peak RPM using a voltage inverter on the other end?

Murlin

Murlin · « **Reply #9 on:** May 19, 2006, 07:55:05 PM »

What I am trying to do is to power a 5-hp motor with the wind. I am trying to figure out how big a machine I would need for that specific purpose.

746watts x 5....

Would that even be possible with the current design of the homebrew machines??

Murlin teh.... hrm I think that's question #3

ghurd · « **Reply #10 on:** May 20, 2006, 05:57:04 AM »

The 17' machines make about 5000W, IIRC. That's big.

I bet they do not do it very often. Or very long.

The HZ will not be 50/60.

Etc.

Murlin · « **Reply #11 on:** May 20, 2006, 08:05:05 AM »

That is alot of power

I wonder if something like this would work?

SparWeb · « **Reply #12 on:** May 22, 2006, 12:27:32 AM »

Ghurd,

Maybe I responded to that too soon. Yes, some flux is "short-circuited" to the rotor before passing through the windings in the stator. But bear in mind that none of the flux lines just trails off in space somewhere. Each line is a closed loop and by mounting the magnets on a steel disk, the lines are concentrated inside it. Those lines connect from one magnet to the next on the rotor, and cross the gap to the opposing rotor more strongly concentrated. Also, they no longer "leak" out the back, meaning that the flux isn't wasted.

There is some lost, as you noticed, but the positives outweigh the negatives.

Does that help?

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