Theorectical benefit of ferro magnet holder for generator

[brandnewb]

I am building a alternator/generator. I am wondering if there is any benefit of having the magnet holder made out of a ferro magnetic conductive material or not.

I have ran some test earlier that seem to suggest it does not but I must admit I probably conducted the experiment in an incorrect manner.

On the other hand when I look at a store bought 3 phase 12 sector magnet pole generator the magnets are housed in a laminated iron sheet holder. So this is what lead me to wonder if that holds any merit.

Any theoretical conclusions are very welcome at this stage.

[Adriaan Kragten]

A PM-generator has an armature and a stator. The magnets are mounted in the armature and the coils are mounted in the stator. The armature is normally made of low carbon iron or mild steel as this iron has a very low magnetic resistance and this gives the highest magnetic flux. As both the magnets and the iron of the armature are rotating, there is no fluctuation of the magnetic flux in the armature and so there are no magnetic losses in the iron of the armature. Mild steel has a very low resistance to a magnetic flux so one shouldn't use ferro magnetic material in the armature as ferro magnetic material has a much higher magnetic resitance than mild steel. Ferro magnetic material is normally used for ferroxdure magnets which have a much lower remanence Br than neodymium magnets.

The coils are mounted in the stator. The are two options, a stator with no iron in the coils like done for most axial flux generators and a stator with iron in the coils like done for generators made from asynchronous motors. Assume that we have a stator with iron in the coils. As the stator is stationary, there will be fluctuation of the direction of the magnetic flux in the iron of the stator when the armature is rotating. This gives eddy currents in the iron of the stator. This reduces the efficiency and the stator can become very hot. Eddy currents can be reduced if laminated iron with electrical isolation in between the sheets is used. The lamination must be in the direction of the magnetic flux and so perpendicular to the direction of the eddy currents. Ferro magnetic material has almost the same magnetic resistance as air and so there is also no advantage of using ferro magnetic material in the stator.

[brandnewb]

First of all, thank you a lot for your contribution.

I am 3d printing my axial arranged magnet holder. I am using PLA filament at the moment but can change to PLA with up to 30% iron powder in the filament. I can also print it hollow so I can fill the whole magnet disk with 99.6+% iron powder CUT 150um if that makes sense.

What would you recommend?

[brandnewb]

the CUT 150 um iron powder I am talking about is not electrically conductive. Only magnetically conductive

[MattM]

Everything I've seen about magnetic fields suggests they do not conduct, only form new fields when they interact with matter or light.  Every new field risks the scattering of the strength within the fluxlines, kind of like a diffuser scatters energy from a light bulb.  In motors they use induction to jump gaps to form magnetic fields.  But magntic fields don't work like electricity.

[brandnewb]

Please help me translate this all please

Do I use a non magnetic conductive housing material for the magnets or should the housing be magnetically conductive?

[SparWeb]

Let me see if I can clarify your own question.
Ferromagnetic materials include iron, nickel and cobalt.
https://www.moleymagneticsinc.com/a-comprehensive-list-of-ferromagnetic-materials/

... when I look at a store bought 3 phase 12 sector magnet pole generator the magnets are housed in a laminated iron sheet holder.

Yes, that's normal.  Most axial alternators do have an iron or steel backing plate to hold the magnets.  So the literal interpretation of your question is yes, most of these alternators have that.

Is there a chance you are trying to ask about something else?

[brandnewb]

Let me see if I can clarify your own question.
Ferromagnetic materials include iron, nickel and cobalt.
https://www.moleymagneticsinc.com/a-comprehensive-list-of-ferromagnetic-materials/

... when I look at a store bought 3 phase 12 sector magnet pole generator the magnets are housed in a laminated iron sheet holder.

Yes, that's normal.  Most axial alternators do have an iron or steel backing plate to hold the magnets.  So the literal interpretation of your question is yes, most of these alternators have that.

Is there a chance you are trying to ask about something else?

Let me try wording it differently.
Why is it normal for axial generators to house their magnets in a laminated iron sheet backing? Is there anything beneficial to be had in terms of power generation potential?

For a DIY generator should the magnets be magnetically attracted to the material these magnets are in? If so why?

[electrondady1]

yes iron backing helps to contain and redirect the magnetic flux

[JW]

On the other hand when I look at a store bought 3 phase 12 sector magnet pole generator the magnets are housed in a laminated iron sheet holder. So this is what lead me to wonder if that holds any merit.

you need to understand what your saying, Magnet circuit magnetic rotors.

[JW]

I almost forgot, EDDEY CURENTS...

[SparWeb]

Why is it normal for axial generators to house their magnets in a laminated iron sheet backing?

Steel or iron backing? Yes that's normal.  Laminated, no that's not common.

Is there anything beneficial to be had in terms of power generation potential?

Yes.  The field that a magnet produces will get stronger when it "flows" through ferromagnetic materials.  If it's just passing through air it's something like 1/10 as strong.  To get the maximum field intensity near the face of the magnet, the other side of the magnet should be attached to an iron backing.  Note that there is also a complete "circuit" being formed here.

[brandnewb]

Just to make sure I am not confusing everybody I will add an image of my current, non ferro housing.



I will start a new topic regarding the arrangement of the magnets at a later stage as that is something I am also struggling with.

But for nor now please picture that there will be coils on both sides of the magnets arranged in an axial manner.

Should I make the magnet holder from a ferro magnetic conductive material and fill the hollow structure with 99.6 iron powder? Or would that be a waste of resources?

Please keep in mind that both the ferro PLA and iron powder are not electrically conductive, only magnetically responsive.

[brandnewb]

wow, that image was of rather low quality ;(

Anyway what one can kind of see there is an array of 96 neo magnets of class N45 with 60x10x5 dimensions. yet oriented to repel rather than a traditional arrangement.

I have self gathered data that might suggest this is a good way to proceed, especially if having iron powder inside of the magnet holder is a good thing.

The magnets are spaced 6mm apart.

There will be 2 disks on each side with 48 coils per phase. The 2 disks will be offset by 60 degrees so we'll end up with 6 phases in total. 3 on each side.

[bigrockcandymountain]

I think if the magnets are between 2 coil plates then you want non magnetic material for the holder.  You want the magnetic flux lines to reach out through the coils as far as possible.  I honestly think the field lines will be curving back to the next magnet and the flux density will be very low in your coils with this arrangement.  That's just a hunch though. 

The usual way to build an axial is 2 rotors of magnets with metal plate backing and a single stator with coils between.  In this case, you want the magnet rotors to be steel and magnetically conductive so that the magnetic field has a nice easy return path back toward the center and the coils. 

[brandnewb]

ok maybe not a new thread then but go on in this one.

I have been using a tesla meter to collect data about magnetic flux strength over several magnet arrangements.

Whether or not the data is to be trusted I can't be sure as my meter just stopped working before it gave wildly fluctuating readings but it I have not found any better data yet ;(

Then, by pure lack of a good understanding and also not being able to find anything online on how to interpret this data I tried my self. I will admit that my way of going about it might be misguided.

(((weaker side value * 2 ) + stronger side value ) / 3 ) * distance between (theoretical zero)middle points.
And then I summed everything up. this is what it looks like


My tentative conclusion is that when repelling we get more flux to play with at closer distances than with traditional. But the hassle of arranging magnets in a repelling manner becomes kind of mute when there is no benefit of having a magnetically conductive housing.

[brandnewb]

I'll give some context to help determine if I have lost course or should plow through on current heading.

Original goal was to try and output a scary amount of voltage at 60 to 120 rpm so I though having 96 poles would be better than 48 or less.

Reason for repelling originally, before I had a Tesla meter, was to be able to reduce the diameter of the magnet disk and thus the whole generator.

It's only after reading several threads here on this forum I came to realize that going for max voltage is not really what one should be looking for. Better to go for max power output at a given rpm.

Ok well, I am always in for changing my mind and willing to admit a bad idea
So given that the whole goal is to charge LifePo4 battery packs rated at 48 volts I though maybe better to wind the coils in such a manner that we end up with 58.4V for each of the 6 phases to be able to use (2) mppt wind charge controllers to charge the battery bank(s)



I am still in very early stages and I am also enjoying experimenting, but given I am close to a year into this project I thought it might be better to ask for advice of people that actually know what they are doing.

[brandnewb]

I almost forgot, EDDEY CURENTS...

Yes, thank you for the addition. Yet I thought having non electro conductive materials that act as magnetically conductive matterials would counteract that.

I figured having 99.6% iron powder and PLA with up to 30% iron powder (both non conductive) might even be better than having a laminated core in where eddy currents are reduced by confinement rather than eliminated all together (or something close to it)

Yet once again, I might be missing the mark here completely though,

[brandnewb]

I meant
"I figured having 99.6% iron powder and PLA with up to 30% iron powder (both non conductive) "
in an electro sense. Of course both materials are magnetically conductive

[JW]

Yes, thank you for the addition. Yet I thought having non electro conductive materials that act as magnetically conductive materials would counteract that.

You should look into some posts of "wire in hand" what we encountered was eddy current in the stator windings and had to use three small wires instead using a thick single conductor.

The reason we found this out was that stators were overheating and melting the fiber-glass resin.

[SparWeb]

I'm sure I'm not following what you're doing Brandnewb, but that doesn't mean you aren't wrong.

Can you draw a cross-section of the machine you're trying to build, like the one I just posted, showing the field lines in complete loops?

A couple of other random thoughts. 
You don't need a "tesla meter" (normally called a gauss meter) to make this stuff.
Field lines are closed loops.  No exceptions. If you can't follow a line one face of the magnet to the other face, try to find out.
Google "halbach array"  Are you trying to build something like that?
Now that you can post images, can you try uploading a photo again?
1000 pixels square usually uploads just fine to Fieldlines and give enough detail to understand the image. 
Windows Paint.

[brandnewb]

Here you can see the concept of the disk
]

here how the field lines are as opposed to traditional.


and here you can see the actual flux lines on one side of the disk over a few magnets.


For the traditional arrangement the measure points that are strongest are along the center of the magnets and drop really fast as we come close to the edge of the magnets which is the weaker measure point. exactly in between 2 magnets the flux is close to 0.

For the repelling arrangement is strongest measure points lie between 2 magnets and the 0 point lie in the center of a magnet.

[brandnewb]

I'll also add where I measured in a repelling arrangement. I hope it helps
For traditional I did the same but then the 0 line lies in between 2 magnets, the edge shows the weaker values and the center of a magnet shows the strongest values.
[ Specified attachment is not available ]

[brandnewb]

the formula i tried applying for repelling was
(((value along stronger point * 2 ) + value along weaker point ) / 3 ) * distance between (theoretical zero) points in mm.

the formula i tried applying for traditional was
(((value along weaker point * 2 ) + value along stronger point ) / 3 ) * distance between (theoretical zero) points in mm.

[brandnewb]

Yes, thank you for the addition. Yet I thought having non electro conductive materials that act as magnetically conductive materials would counteract that.

You should look into some posts of "wire in hand" what we encountered was eddy current in the stator windings and had to use three small wires instead using a thick single conductor.

The reason we found this out was that stators were overheating and melting the fiber-glass resin.

great, thank you. I'll go look for that thread

[MattM]

Are you going for some sort of radial motor?  I ask because your magnet alignments are unusual.

If it was meant as an axial then it seems you are putting a lot of effort into creating flux into the rotor.  Without a third magnet in between the gaps there isn't much benefit, since your individual magnetic flux lines overlap one another and focus 90 degrees in the wrong direction.  A third magnet would give you sort of a Halbach array, pushing your flux lines perpindicular to the rotor.  Otherwise, depending on the strength of the magnets, you flux lines may be working against each other for an axial and only emit half as wide or less from the rotor.  I fear you may go to all that work for little result.

Look at Sparweb's example.  He shows two rotors with magnetic poles going perpindicular to each rotor.  Instead of colors to show magnetic poles he used arrows.  The rotors augment each other to enhance flux lines that are useful for an axial.

[electrondady1]

what i  see is a common mistake on what the optimum lay out is for an air core alternator, consisting of a single mag rotor disk  in the center and two stator disks on the outside.(been there, done that)

the optimum lay out for an air core alternator is with two mag disks on the outside with iron backing containing all flux  and a single stator  on the inside.

 in that way, the copper conductor is  crossing an area of hi flux density  between the two mag rotors.

 

[brandnewb]

Are you going for some sort of radial motor?  I ask because your magnet alignments are unusual.

If it was meant as an axial then it seems you are putting a lot of effort into creating flux into the rotor.  Without a third magnet in between the gaps there isn't much benefit, since your individual magnetic flux lines overlap one another and focus 90 degrees in the wrong direction.  A third magnet would give you sort of a Halbach array, pushing your flux lines perpindicular to the rotor.  Otherwise, depending on the strength of the magnets, you flux lines may be working against each other for an axial and only emit half as wide or less from the rotor.  I fear you may go to all that work for little result.

Look at Sparweb's example.  He shows two rotors with magnetic poles going perpindicular to each rotor.  Instead of colors to show magnetic poles he used arrows.  The rotors augment each other to enhance flux lines that are useful for an axial.

I'd like trying utilizing both sides of the magnets. So the coils I have planned are 3 phase per coil disk/stator. Both stators offset by 60 degrees from each other to create 6 phases in total.
This is why I had hoped having an magnetically conductor magnet housing would better conduct the flux towards both sides of the magnets but I was unable to demonstrate that with earlier measurements I made.
It could be though that my readings with the Tesla meter are not reliable at all so that I am not sure what to believe anymore ;(

I am currently trying to 3d print a structure sturdy enough to be able to spin the magnets around at 60 to 120 rpm to see how much winds I'll need per coil to get to 58.4 V at 60 or 120 rpm.

I am not sure yet what is better in terms of rpm, 60 or 120, to reach the target voltage. But I really would like to prevent the rotor (magnet disk), and turbine that will serve as the drive for the rotor, having to spin faster than 120 rpm due to safety concerns with turbine blades in an urban setting.

[brandnewb]

what i  see is a common mistake on what the optimum lay out is for an air core alternator, consisting of a single mag rotor disk  in the center and two stator disks on the outside.(been there, done that)

the optimum lay out for an air core alternator is with two mag disks on the outside with iron backing containing all flux  and a single stator  on the inside.

 in that way, the copper conductor is  crossing an area of hi flux density  between the two mag rotors.

yes indeed it sems I am going to that route again. Could you please share any of your date, however untrustworthy, to support your conclusion?

I for one only have data that seems to support a 6 phase disk is fruitful. Yet again I will admit I might be misguided here.

[brandnewb]

But May I please ask everyone to stay on the current question at hand? Whether a housing of non conductive in magnetic terms is better than one that is? Given the current context

[brandnewb]

ugg, I meant to say that I have no better data yet.

current data suggests that going for repelling at +-6mm spacing is fruitful. Especially when going for a 2 x 3 phased disk of coils.

I am here to find out how I missed the mark! Or perhaps plow through.!!!

[SparWeb]

I'll grant that you can aleays try something different and see what happens.

Using what you have now, you can try this:

___________ steel disk

O  O  O  O  O stator coil disk

#  #  #  #  #  magnet disk

O  O  O  O  O stator coil disk

___________ steel disk

The axle must make the two steel disks turn with the mag disk, i.e. 3 disks turning on the same hub.  The 2 stators remain still.

The size of coils in the stator should match the magnet spacing as exactly as possible.  The densest flux lines are Between magnets, now, which is a little counterintuitive to me.  I just drew a flux line circuit through these parts and the loops close.  So you'll get something.  Can't say how much though.

[electrondady1]

 it looks to me that your magnet layout is unconventional.  it appears that you are placing the magnets on their edge. it appears the poles of the magnets are facing each other