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Forum Index : Windmills : N35 vs. N52

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DaViD

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Joined: 14/01/2009
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Posted: 03:45am 27 Mar 2009

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Hi guys, Has anyone used the N35 and the N52 in the same application to see what the performance differance was? And if so did you make any tables showing the differance?

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niall1

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Joined: 20/11/2008
Location: Ireland
Posts: 331

Posted: 05:00am 27 Mar 2009

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hi David

if you mean switching to the higher grade in a machine where the prop was fairly well matched to the alt already (existing mags)

then then the effects migh,nt be so good

now the alt will generate at a lower rpm which would propabely stall out the prop giving less power overall..

niall

DaViD

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Posted: 05:11am 27 Mar 2009

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Thanks, that makes sense assuming the cogging would be a (lot) higher?

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niall1

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Posted: 05:59am 27 Mar 2009

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sorry i was thinking along axial flux lines , but your right on an iron core motor that cogged maybe just a small amount you could create a cogging beast that might hold down the prop completly in low winds

just sometimes less is more

Edited by niall1 2009-03-28

niall

DaViD

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Posted: 09:17am 27 Mar 2009

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Oh yes! less money! my wife screams

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imsmooth

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Joined: 07/02/2008
Location: United States
Posts: 214

Posted: 11:23am 27 Mar 2009

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If you are using the F&P rotor you should not go above N35 as the magnetic
forces could begin to warp the rotor when they interact with the iron cores
in the stator. I found N35 way sufficient, and the iron current losses will
start limiting any gain.

oztules

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

Posted: 12:58pm 27 Mar 2009

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In an axial flux.... more is better, as you can use less turns for the same cut in, and introduce resistance into your load lines rather than the stator to shift the heat away from the genny. (must have resistance somewhere to be able to generate usefully with wind)

For induction conversion... more is better, even completely saturating the stator core is better than not... If your rewinding, it is all good, if you are stuck with weak original windings, matching your battery bank may be problematic but more flexibility with using different wiring schemes with the available coils is more likely with stronger than weaker magnets.

Matching the load to your turbine is still the paramount concern, but this whole business relies on wire moving through magnetic fields... bigger the fields, the less wire.. the less resistance, and everything good follows from this.

Bigger magnets allows you to design for less back MMF, less armature reactance, less inductive reactance, less resistance, less heat... etc........in short, less synchronous impedance.

But you still need to match your prop to your load to be of benefit (as Niall points out.)

In an F@P, Imsmooth and Bruce have the runs on the board, and it appears mechanical issues are relevant, and iron loss goes up with stronger magnets.

The iron loss can be compensated for with bigger blades as the cut in will drop anyway, so may not be a real problem if you can change blades.... but the rotor case falling to bits is more of a problem.

........oztules

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

niall1

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Location: Ireland
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Posted: 01:29pm 27 Mar 2009

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pretty neat....never thought about the options on re wiring the stator

if its an axial you might even be able to run it with a bigger air gap (less chance of coming in contact with the stator especially on large rotors ).....mmmmm Edited by niall1 2009-03-28

niall

GWatPE

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Location: Australia
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Posted: 01:54pm 27 Mar 2009

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The rotor distortion problem seems to happen with the externally caged AxFx mills, with thin rotor disks. I believe someone has an AxFx unit with 1" thick 2" rounds with 1/4" rotor plates. The higher magnet strength probably comes at a significant cost, for the 40% stronger field. I have only seen 3mm thickness mags at >N50 strength, and these only had 80C rating. I would opt for the higher temp rating. I use 120C rated mags.

For a test unit, to see what could be possible, without budget constraints, then the strongest mags would be the go. Reality will come and bite eventually.

Gordon.

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DaViD

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Posts: 120

Posted: 06:09am 28 Mar 2009

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Thanks guys I'm going to try the 2" X 1" X 1/2" N54 rectangle mags. on a dual stator config. to see if I can make a dual work for me. I'll go ahead and order the N35 also. If I dont need them on this project I can always use them on another.

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rothko

Newbie

Joined: 27/02/2009
Location: Netherlands
Posts: 8

Posted: 08:16am 28 Mar 2009

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Which grade's the most cost effective, in a magnetic flux/$ sense?

DaViD

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Posted: 09:25am 28 Mar 2009

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Hi rothko, only from a flux vs. $$ the N35 mags would be better in my opnion.

If your not living on the edge your taking up to much space!

GWatPE

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Posted: 11:40am 28 Mar 2009

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Hi DaViD,

I found the higher magnet strength was not cost effective as well.

I am not real keen on the rectangular magnets on an AxFx config. My prototyping with magnet ring diameters below 12" showed that rounds are better use of the space. You can get more usable magnet volume into the same space. Above 36" rotor diameters, there may be merit in rectangular blocks as the segmentation gap voids are not as pronounced. This size would be a difficult undertaking to make.

Gordon.
Edited by GWatPE 2009-03-29

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DaViD

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Location: United States
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Posted: 12:47pm 28 Mar 2009

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Hi Gordon, When you say rounds are you meaning disks or the washer type with a hole in it?

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GWatPE

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Posted: 12:39am 29 Mar 2009

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Disks are the norm. No point in having a hole in the middle. Air can't produce an emf.

Gordon.

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DaViD

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Posted: 04:12am 29 Mar 2009

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Gordon what size disks are you using?

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GWatPE

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Posted: 11:42am 29 Mar 2009

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Hi DaViD,

All my info is on the F&P@PE thread.

Gordon.

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DaViD

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Posts: 120

Posted: 11:10am 30 Mar 2009

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Hi Gordon, i'll get some of the 2"x1/2" disks and try them out they seem
to be cheaper than most others too

If your not living on the edge your taking up to much space!

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