TheBackShed.com

Forum Index : Windmills : cog free coil/ magnet ratios?

Author

Message

Tinker

Guru

Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 01:19pm 07 Jan 2010

Copy link to clipboard

Print this post

The Shibura alternator I got here does not cog at all, much less than the F&P converted to 7 phase which I also have to experiment with.
I am wondering if there are other coil/ magnet ratios that produce no cogging?

For those who are unfamiliar, the Shibaru has an outside 12 coil stator on laminated iron pole shoes. They are connected in 3 phase star (4 coils in series).
The rotor within has also a laminated construction with 10 pole shoes. A PM of unknown shape within magnetizes these in a N/S/N/S... alternating configuration.

I ask this question as it occurred to me that one could use a similar ratio on AXFX alternators with the inclusion of iron filings encapsulated in epoxy, within the coil centers.

Is this a crazy idea or would it provide some improvement to the magnetic path?

For a reasonable number of turns in the coil one needs very powerful magnets (expensive and dangerous), would the iron filing idea permit a smaller magnet for an identical coil gap?

I'm looking forward to read your comments.

Klaus

oztules

Guru

Joined: 26/07/2007
Location: Australia
Posts: 1686

Posted: 10:08pm 07 Jan 2010

Copy link to clipboard

Print this post

Not crazy.

Jerry of fieldlines used a 14:11 ratio for an axial flux with iron cores.

It was designed for mechanical /cogging cancellation, not three phase. Each coil in this case is independently rectified, but he claims very good figures for ferrite magnets in this configuration.

Without iron cores, ferrites do a poor job in an axial flux configuration.

...........oztules

Village idiot...or... just another hack out of his depth

Dinges
Senior Member

Joined: 04/01/2008
Location: Albania
Posts: 510

Posted: 11:07pm 07 Jan 2010

Copy link to clipboard

Print this post

[quote]I am wondering if there are other coil/ magnet ratios that produce no cogging?[/quote]
There is a lot of information in this site:

http://www.powercroco.de/rasten.html
http://www.powercroco.de/Kombinationstabelle.html

" Systeme die dem klassischen Aufbau folgen 3:2 (Grundwellen-Motoren - wie alle 2poler BL, 3 Spulen / 2 Pole N und S) 3:4 (2. harmonische Motoren mit 3 Spulen / 4 Pole, N-S-N-S)oder allgemein: 3n zu 2p oder 3n zu 4p,(6N8P; 12N16P)sind immer stark rastende Motoren.

Aus der Suche nach wenig rastenden Kombinationen resultierten dann die Motoren mit 12 Nuten und 14 oder 10 Polen (LRK), oder auch 9 Nuten mit 8 oder 10 Polen (CDR-Motoren).
Das trifft nat�rlich auch auf deren vielfache (18N16 oder 20P) zu!"

As he says, there are combinations that produce *less* cogging (no cogging doesn't seem to be possible using this technique)

http://www.powercroco.de/theorie.html

With apologies to the non-German speakers, but Tinker's name suggests a German-speaking heritage, so I assume he won't have too much trouble reading it.

Peter.Edited by Dinges 2010-01-09

GWatPE

Senior Member

Joined: 01/09/2006
Location: Australia
Posts: 2127

Posted: 11:59pm 07 Jan 2010

Copy link to clipboard

Print this post

Surely the benefits provided by NEO magnets is worth the effort to handle them with a bit of care during building, without resorting back to iron cores for DIY windmill applications.

become more energy aware

Tinker

Guru

Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 01:13pm 08 Jan 2010

Copy link to clipboard

Print this post

GWatPE said Surely the benefits provided by NEO magnets is worth the effort to handle them with a bit of care during building, without resorting back to iron cores for DIY windmill applications.

I agree Gordon, just thought there may be a way to make them even better with NEO magnets (especially the smaller ones I am playing with presently).

Dinges, thanks for posting that German article, you were right, I was raised in that language (in Austria) but it has been many many years since I dealt in German technical terms.
I did get the gist that its not quite as simple as I though initially, lots of factors come into play. I think with my motor its the rather small gap at the ends of the "hammerheads" on the rotor that reduces the cogging. The stator is wound & connected as the little calculator suggests.

I think the 11 coil/ 14 magnet ratio Oztules mentioned might be worth tinkering with. If it works well with ferrite magnets it could be even better with NEO's

Klaus

Print this page

To reply to this topic, you need to log in.