Non air core coils question.

[Dark Alchemist]

I posted this on another forum but apparently the most active parts of their forum is things that break the laws of physics, thermodynamics, etc... and this went unanswered there so I will ask it here.

I haven't kept up much with the changing world of cores so I started to look around and noticed something new to me called Amorphous metal.  This stuff is pretty darn nice and I would think would help with anything that has windings.

I am not, and have never been, a fan of open cores for anything less than about a megahertz and if your wind turbine is spinning around fast enough to be in the megahertz range then I gotta see it, lol.

Anyway here is some technical info about this stuff (it seems China is already converting their grid over to it): Technical advantage

Where typical ferrite cores can only operate up to a flux saturation level (Bsat) of 0.49 Tesla, an amorphous metal core can operate at 1.56 Tesla. Combined with operating at permeability similar to high-end ferrites and the flexibility of manufacturing large cores sizes these cores can be an ideal solution for many of these components.

{I'm sorry but we don't allow commercial links until you've established yourself: can you find an academic reference instead maybe?  DamonHD}

What do you think of this for cores in our windings to help produce even more energy or at least reduce our magnet counts (the most expensive part I found)?

[joestue]

the problem with iron cores is they add a whole nother level of skill required to pull it off.

motor conversions are about the only iron cored machine practical for DIY folks who don't have access to a milling machine. all you need is a lathe to make a motor conversion.

However all you need is a small furnace to make a wound rotor conversion for an induction motor, to melt out the aluminum.
however what i found is the cores are undersized by a factor of 2-4, (there's a reason they need a fan to cool them)

but aside from all that,  you do not need expensive amorphous cores to get 1.5T field strength.
I have some 400Hz transformer cores that ran at 1.7T.. from scrapped military transformer stock. 4 mill strip wound silicon steel.

[Dark Alchemist]

Yeah, military and space grade stuff will always be better but trying to grab some in enough quantities is another story, and lets not even talk about the prices for that stuff new, lol.

edit: To answer DamonHD I don't have a link on this new metal only companies (there are tons of them) that make it.  Seems China is huge into this and are already converting their city grids over to it.

[Flux]

Like most things it will depend on availability for one off construction.If small motors start being produced with this material it may be possible to get cores ( likely still a motor conversion but with a different type of core). I don't think it likely that you will get a one off core at a finite price.

If this stuff eliminates most of the core loss associated with laminated iron cores it may be of advantage in wind machines, the core loss is a seriopus issue and at present the best way to avoid it is not to use an iron core.

Cogging will no doubt be an issue but can be dealt with by suitable design.

You will still run into the leakage reactance problem and that could be something of an issue with ferrite magnets. Adopting some form of mppt will mitigate much of this trouble but you are trading the cost of a mppt converter for reduced magnet costs, something you can alrerady do with present designs.

Only time will tell whether this will be cost effective for one off use, it does look to be the only thing to challenge laminated iron cores that is worth looking at, ferrite and powdered iron and similar things have never been worth considering.

Flux

[Dark Alchemist]

Yes, and I know of no one around me who can make laminated cores so I know that I am stuck using open air cores but honestly they aren't all that efficient when we Turbine builders need the best efficiency we can muster.

The cogging issue is the only issue I thought about after reading about this stuff from all over the web (just Google the stuff there is tons of companies but not really anything to chomp into in the way of Academia that I could find) but I am unfamiliar in how to minimize it by what you call a suitable design (have any info or a site I could look at?).

I do think that if China is converting all of their existing laminated iron core stuff over to it then something big is up and that piques my interest since we are dealing with creating power as well just not on the mega/giga watt scales like a Chinese power plant does.

Now cost is something I couldn't find but I think it is due to the one off type deal I am after and because this is still pretty new.

You gotta admit that 1.5T field strength out of something that is more cost effective than what is currently available is intriguing.  Sure we can get more than that but you need to be in the Aerospace field or the military and that stuff isn't cheap by a long shot.

[Mary B]

http://materialsworld.utep.edu/Background/Inorganic%20Chemistry/PDF%20files/Amorphous%20Metal.pdf

[birdhouse]

The cogging issue is the only issue I thought about after reading about this stuff from all over the web (just Google the stuff there is tons of companies but not really anything to chomp into in the way of Academia that I could find) but I am unfamiliar in how to minimize it by what you call a suitable design (have any info or a site I could look at?).

search the board for skewed magnets and or motor conversions.  you'll see the magnets being placed at a slight angle off parallel from the shaft.  i don't think it eliminates cogging, but makes it a whole lot better. 

adam

[Dark Alchemist]

http://materialsworld.utep.edu/Background/Inorganic%20Chemistry/PDF%20files/Amorphous%20Metal.pdf

Interesting but not exactly what I was looking though my link was eaten by the mod so most don't know what I am talking about.

Good info and since it said it isn't new (citing 1950) something had to have changed for China to be massively converting over and I doubt the stuff in Golf clubs and Tennis Rackets is what they are using though I could be wrong too, lol.

[Dark Alchemist]

The cogging issue is the only issue I thought about after reading about this stuff from all over the web (just Google the stuff there is tons of companies but not really anything to chomp into in the way of Academia that I could find) but I am unfamiliar in how to minimize it by what you call a suitable design (have any info or a site I could look at?).

search the board for skewed magnets and or motor conversions.  you'll see the magnets being placed at a slight angle off parallel from the shaft.  i don't think it eliminates cogging, but makes it a whole lot better. 

adam

Yes, I have seen that in a slant like the spirals on an AC fan motor so roughly a 45 degree angle but didn't know why.

[birdhouse]

Yes, I have seen that in a slant like the spirals on an AC fan motor so roughly a 45 degree angle but didn't know why.

45 degrees is really steep angle.  i think most folks go like 7 or 12 degrees??  i believe there's actually a formula for the angle based on how many poles the motor has??  starting to get beyond my knowledge base

adam

[Dark Alchemist]

Yeah, something I saw had 45 but I can't remember what it was now, but when I just took my cooling fan apart it was in a spiral type shape around the silver armature inside but not at 45 degrees more like 10-15 it looks like.

So, on a new design using N52 bar magnets (2x1x.75) I wonder if I should angle them?  Hmmmm.

[joestue]

the angle sets the slip and the torque curve.

smaller motors have higher angle for a multitude of reasons, the first of which is torque density.

[Dark Alchemist]

the angle sets the slip and the torque curve.

smaller motors have higher angle for a multitude of reasons, the first of which is torque density.

Well, how do we know what to use on a PMG?  I could whip out FEMM but I haven't found a gui frontend for it that I like and I blow in graphical stuff.

[electrondady1]

 the angle the mags are skewed is dictated by pole width and coil width.

[joestue]

The magnet skew?
the general advice is to skew it across one tooth width.

[Dark Alchemist]

Hmmm, tooth width, pole width?

Coil's I.D. is 1/2 the width on the bar magnets and the O.D. is about 1/4 inch wider.  Magnets are 2x1x.5 (or .75).

[bob g]

in my experience, the skew is just a bit more than the width of the slot in the stator core.

skew for the most part as it relates to alternators is used to improve waveform and to eliminate notch effect as seen on the sine wave.

you want enough to eliminate the notch effect and clean up the wave form, but not so much as to alter the wave shape and cause other issues (which i can't remember what it is, but iirc relates to efficiency concerns due to coil cancellation issues and the introduction of distortion to the wave form)

you may need a bit more than this strict guideline to improve cogging, but i would not go much more than the width a slot myself. i would address the remaining cogging in other ways rather than increase skew.

bob g

[Dark Alchemist]

So basically skew it where the right corner top side and the bottom corner left side never are outside the coil radius?