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Another Silly Idea
By ghurd, Section Mechanical Posted on Fri Sep 2nd, 2005 at 03:58:02 PM MST
Anyone see problems?

Hi all,
I'm still playing with small stuff and trying to minimize tooling, parts and complexity.
Noticed how the ready to strip microwave transformers look something like Ed's little kit, but with nice laminations and all ready wound coils. Ready to strip meaning the welds were ground away, and the tops knocked off. There is a lot of variation in the turns and wire gauge of the transformers I have here now.
Inspired by this...
http://wondermagnet.com/other/gentest.html
I have to think that single rotor setup had 'problems'.
Like no return path for the flux. Kind of poor laminations. Kind of long.
But I don't know. But the numbers still weren't too bad!
Here's the plan. I don't think it needs a whole lot of explaination.
I think I can get around the cogging with creative magnet placement.
I hope thats not sideways :/

It makes some kind of sense that the outer magnets should each be half over the transformer, when the middle magnet is centered. Tell me if thats wrong.
Any ideas why this one will not work? Or how to make it work better?
Should the transformers be epoxied to a 4x4 for testing, to give some space between the transformer and drill press table?
I have done almost similar projects, many involving shaded pole motors, but a majority did not work. Not even a little!
Thanks,
G-

Another Silly Idea | 9 comments (9 topical, 0 editorial)

Re: Another Silly Idea (3.00 / 0) (#1)
by bob g on Fri Sep 2nd, 2005 at 10:08:11 AM MST
(User Info)

i dont see any reason it wouldnt work,

also should work with coils on each leg, or rather it definitely would work with coils on all legs, just alternate the directions.

am i right, seems very workable to me

bob g

Re: Another Silly Idea (3.00 / 0) (#2)
by jimjjnn (jimjjnn at yahoo dot com) on Fri Sep 2nd, 2005 at 11:02:41 AM MST
(User Info)

I think I would try it with coils on each leg of lams.Take coils off other xfrmrs since they come apart with slight effort.You can always put the coils back on the other xfrmrs if it doesnt pan out.
I do like your thinking and the way you do things. Makes most interesting reading as do most posts on the board.
Jim Denver,CO
[ Parent ]

Re: Another Silly Idea (3.00 / 0) (#3)
by Flux on Fri Sep 2nd, 2005 at 11:49:20 AM MST
(User Info)

No it's not a silly idea, it's what Pixii did when he improved Faraday's disc and made the first practical dynamo.

In the form you have drawn it, it is used for high tension magnetos. If you wind all the legs and stack a ring of them it becomes a motorcycle type alternator or a F&P motor.

With a single core I doubt if there will be much difference if you wind all 3 legs, as there is only limited space and you will have 3 smaller coils.

The main snag with this type of iron circuit is that cogging is virtually inherent and the more it cogs the better the output .

If you try to reduce the cogging you will almost certainly reduce the output so it will have to be a compromise. I think that you may be able to space several cores round the circle and critically space them to reduce cog, and still keep the output from each.

If microwaves have the same size cores as they do here I would hardly call it a small project and there are many better ways to get a similar output without the snags. for small outputs with small transformer coils it may d
be a good idea.

This type of core design does have a lot of leakage reactance and the output tends to level off to constant current, which is why it is used for motorcycle alternators.

Somewhere I have a reference to a large one built with transformer cores at a
university but I can't find it at the moment.

Flux

[ Parent ]

Re: Another Silly Idea (3.00 / 0) (#4)
by ghurd on Fri Sep 2nd, 2005 at 01:05:50 PM MST
(User Info)

Thanks Guys,

It just seems too simple NOT to work, but so did some similar tries with a more radial than axial idea.
Complete and udder failures! Every one. Like not even worth connecting a red LED, just in case...
Still have NO idea why at least a couple didn't work.
I would post a couple photos, but they have all been recycled into Kia SUVs by now.

Thought about 2 or 3 transformers to reduce cogging, and maybe even make it 3 phase. About 8 transformers, but no 2 even close to the same.

Somethin very strange and oddball, like the 4 magnet/6 coil idea, may work.

Thought about winding the 2 outside legs, but figured the flux dansity was only half.
Then thought about winding the 2 outside legs, setting the magnets different, and getting a 2 phase output. Not sure about the cogging issues, and so it may work better, cogging wise.

The microwave magnets may be the right size! A little lame on the flux maybe. Just now thought of them.

This is kind of a sawblade idea to use up some strong but strange magnets.

Flux,
I'm in the US.

All my transformers seem to be from about (mostly) 3x3x3"-ish to a 6x6x4.5"
(a monster from a microwave with mechanicial timer switches and #10 primaries,
but all the magnets seem to be only 2 sizes, one size just thicker than the other).

If leakage reactance becomes an issue at all, it will be a success.

With the heavy wire and my blades, I would expect it to stall before leakage reactance has any real effect. But I don't know...

Everybody,

Will the transformer be adversely effected by placing it directly on the cast iron drill press table? I kind of figure it won't matter much until I get near saturation, at which point leakage reactance will come into play. Again, I don't know.

Anyone with thoughts related to one magnet over the center, and 2 magnets each 25% over the outside legs? Related to reducing cogging. I know it will reduce output.

G-

[ Parent ]

Re: Another Silly Idea (3.00 / 0) (#7)
by bob g on Fri Sep 2nd, 2005 at 10:50:46 PM MST
(User Info)

"Will the transformer be adversely effected by placing it directly on the cast iron drill press table?"

i dont think the cast iron table will effect much for testing, mainly because the magnetic circuit is strongest thru the core. not much is going to escape into the cast and have any serious eddy current concerns. (imho)

bob g

[ Parent ]

Re: Another Silly Idea (3.00 / 0) (#8)
by ghurd on Tue Sep 6th, 2005 at 03:12:03 PM MST
(User Info)

Hi Flux!

You always get me thinking.

""If microwaves have the same size cores as they do here I would hardly call it a small project and there are many better ways to get a similar output without the snags. for small outputs with small transformer coils it may be a good idea.""

I'm not really looking for a lot of power.
These have a lot of turns of heavy wire.

Does this sound workable?
If I open the air gap, to reduce magnetic and electrial induced cogging,
it will reduce the output for sure.

Do you figure the wider air gap and lower output will balance out somewhere?

Or should I just forget about it until or if I get at least 3 matching transformers?

G-

[ Parent ]

Re: Another Silly Idea (3.00 / 0) (#5)
by thunderhead (mail me from my homepage!) on Fri Sep 2nd, 2005 at 01:19:55 PM MST
(User Info) http://www.simon.richardson.net/mailme.htm

It doesn't look silly to me either. But what do I know?

It makes some kind of sense that the outer magnets should each be half over the transformer, when the middle magnet is centered. Tell me if thats wrong.

Surely you want one core per three magnets. Then you'll wind the other way for alternate cores, as the first core will be NSN, and the second SNS, and then NSN, and so on.

A possible way to reduce cogging might be to use one fewer or more magnets than the 3:1 ratio suggests. So if you used 8 magnets and 3 coils, only one coil could be pointing at a magnet at one time, and so it would cog in 24 places, so turning more smoothly. The output would also then be 3-phase.

Re: Another Silly Idea (3.00 / 0) (#6)
by ghurd on Fri Sep 2nd, 2005 at 02:10:17 PM MST
(User Info)

I was kind of leaning toward 1 core, with 2 (total, 1+1/2+1/2=2) magnets in the same active area.
Or maybe even 1 core with 5 magnets, but thats another story, that I can't even begin to draw yet.
(but hey. That 6 coil and 4 magnet thing worked!!! And thats 2 magnets with 3 cores. Kind of sort of.)

I had not yet considered 8 magnets and 3 coils.

[ Parent ]

Re: Another Silly Idea (3.00 / 0) (#9)
by ghurd on Fri Sep 9th, 2005 at 08:42:21 AM MST
(User Info)

I found "about" the same thing with a better drawing by Hannu, 2/3 down the post.
http://www.fieldlines.com/story/2004/6/7/21190/34164
G-

Another Silly Idea | 9 comments (9 topical, 0 editorial)

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