How to determine the limits of a coil / magnet configuration

[Mary B]

Thank you Ed,

This means the world to me!

So I have been able to figure out where that image came from or at least determine that it is also used by a Vietnamese seller of PMA kits.
https://www.blogdiengio.com/p/nhan-lam-bo-kit-may-phat-ien-500w-1kw.html

here is a translation of what is written in the context of that image
"Get generator kits for 500w, 1kw, 2kw, 3kw, 5kw

Do you want to make your own generator but don't have time or are you simply lazy? Let us help you. The machines we make are close to the capacity and suitable for where you live. Please contact Lam Nguyen"

My complaint to sellers like this and to the endless videos being shared online that they always fail to mention how it was determined to have a certain rating.
That was the origin of my question to you in the PM magnets to watts.
Let alone it says nothing about the coil shape and the reasoning behind that coil shape.

And of course I trust you and I will listen to you and will set this up I just fear the RPM need to be really high in order for the voltage produced to be of any use.
But as you stated I do lack a lot of understanding yet so let us just go at it and see where this leads us.

So step 1 would be is to eyeball the dimensions of this setup yes?
I am having difficulties guessing as I do not see a clear reference point to work from.
Step 2 would be sourcing these type of magnets. And I can I have already checked.
https://www.supermagnete.nl/blokmagneten-neodymium/blokmagneet-40mm-40mm-20mm_Q-40-40-20-N
if we opt for a 60kg holding force

or we can go a little stronger with something like this
https://www.supermagnete.nl/blokmagneten-neodymium/blokmagneet-50.8mm-50.8mm-25.4mm_Q-51-51-25-N

Now obviously the relationship between cost and power is lost but that does not matter in the pursuit of science.

That Vietnamese design is a copy of the one created by the founders of this forum, coil shape and number of turns was came by experimentally... and with a little math as Ed showed you above. Formula is out there for magnetic flux, more math than I care to do, or use one of the simulators many pointed out to you... that bypasses the hard math I hate! Bad enough I have to do math designing electronics!

[Mary B]

in the meantime I have already a tentative conclusion that indeed a 1mm wire is the way forward as opposed to smaller.

What I did is have a coil of 1mm wire with 10 winds and a coil of 0.4mm wire at 40 winds.

Coil shape was narrow like in the double density tests.

When at around 8 Hz the 0.4 coil did around 160mV and the 1mm coil did around 48mV.

Then I hooked up each coil separately to the CVCC and fed in the voltage level they produced at 8Hz.

Then I measured the field strength at 10mm distance on both.

The 1mm coil had 16mT and the 0.4 coil had 8mT.

Unless I am tackling this wrong I think we have a clear winner {1}for when winding narrow.

But in the process just now of trying a coil shape that is matched to the magnets at 3.75 interval then this happened.

(Attachment Link)

at 3.8 Hz the 10 winds 1mm coil did around 100mV and the 40 winds 0.4 coil did around 410 mV.
at 100Mv DC the 10 winds 1mm coil produces a field of 25mT in the center at 10mm distance. the field drops sharply when moving to the coil legs.

at 410mV DC the 40 winds 0.4 coil also produced a field of 25mT in the center at 10mm distance. the field drops sharply when moving to the coil legs.


Now I think it is a matter of finding the sweet spot of how thick we can get wires. 1mm might indeed be the absolute minimum.



{/1}

{2}this website actually does tell a lot about the coil and shape. so something to hold on to and work from in terms of dimensional reference point.{/2}
{3}albeit that the coils seem to vary from picture to picture. So I am not sure which one was intended for the rotor configuration and which KW rating was attributed to it.{/3}

Don't worry about coil magnetism! They do not generate magnetic fields when in use!

[brandnewb]

  Ok so now I am thoroughly confused.

I was still operating under the assumption that we are looking for some kind of breaking force ability. As it was stated here earlier it is the mechanical resistance the PMA needs to overcome to actually provide power.

Or should we perhaps concur on a different vantage point? Another,  with a more wide consensus?

I am open to any and all as long as I can get rid of this fog of war that is obscuring vision for the grunt soldiers like my self.
I am sure that the generals up top have 20/20 vision but I am defending my mates here at the front line.

[brandnewb]

pfff a sigh of relieve.

I had the probe on wrong and also the wire ends weren't sanded enough to make the probe latch reliably.



So false alarm thus far. Still no signs of interference.

BTW Mary, if all results are already in of this design, Ed suggested me to take a look at, then how can I be of help giving those a once over?

Is it that perhaps making use of a tesla meter can give some new insights?

Anyways may I please have the link to where this work has been done before me so I can learn and potentially see what Ed meant with how I can be of benefit?

{1}the reason why the waves are rather erratic is most likely because the wires were vibrating as they were banged at while the magnets spun over them.{/1}

[MagnetJuice]

brandnewb . . . . . . . . . . SLOW DOWN

I don’t know where you got the idea that I suggested a Vietnamese website.

That image of the rotors that I posted is from a big 4kW alternator that Dan Bartmann built years ago. It is just an image to show a setup with 2 rotors that you can build and use for testing.

The rotor setup that you build for testing should have only 8 magnets per disk.

The magnet wire should be between .9mm and 1.3mm. No smaller or bigger than that. That wire size can also be used for the big alternator for your VAWT.

The magnets that you showed on the links are the wrong proportions.

A magnet like this will work for testing and will also work for your big multipole alternator for your VAWT.

https://enesmagnets.pl/en/permanent-magnets/neodymium-sintered/block-magnets/50-x-20-x-20-n35-ndfeb-neodymium-magnet.html

If you use 8 magnets per rotor, the steel disks should be about 280mm diameter, and the thickness should be 9 or 10mm.

If you build this rotor setup, make sure that you build it in a way that you can adjust the air gap.

For now, forget about Teslas, braking force and terms like that.

Start thinking number of turns, resistance, air gap, RPM, volts and amps.

Ed

[JW]

Philosophy of logic


https://en.wikipedia.org/wiki/Philosophy_of_logic

[Mary B]

pfff a sigh of relieve.

I had the probe on wrong and also the wire ends weren't sanded enough to make the probe latch reliably.

(Attachment Link)

So false alarm thus far. Still no signs of interference.

BTW Mary, if all results are already in of this design, Ed suggested me to take a look at, then how can I be of help giving those a once over?

Is it that perhaps making use of a tesla meter can give some new insights?

Anyways may I please have the link to where this work has been done before me so I can learn and potentially see what Ed meant with how I can be of benefit?

{1}the reason why the waves are rather erratic is most likely because the wires were vibrating as they were banged at while the magnets spun over them.{/1}

With air core coils cogging isn't an issue to worry about! Why iron core has been tried and not used.

For what you are doing get an F&P setup here http://www.randysworkshop.net/order.html and use it to play with your mechanical design, once that is perfected THEN see if you can improve on the alternator part of the equation! The F&P as is will crank out some decent voltage at low RPM, I spun one up by hand and lit a 100 watt 120 volt light bulb! 60RPM = 18 volts! https://www.fieldlines.com/index.php?topic=149388.0 Gear up your design to spin it faster and see better output! Stack 2 or even 3 assemblies if you have the torque and series it for low RPM higher voltage...

Playing with an F&P will teach you about cogging too and how much torque it takes to over come it.

[brandnewb]

Affirmative Sir,

I have ordered now 16 of those magnets and will now look for the disks. Are iron disks also ok? Easier and less expensive to source from here.

I will also purchase 1.3mm wire.

Thank you all guys for pitching in! I would love to have something producing power before the 3 year mark

Optimizations can always happen after that fact, should there be time left.

The rotor setup that you build for testing should have only 8 magnets per disk.

The magnet wire should be between .9mm and 1.3mm. No smaller or bigger than that. That wire size can also be used for the big alternator for your VAWT.

The magnets that you showed on the links are the wrong proportions.

A magnet like this will work for testing and will also work for your big multipole alternator for your VAWT.

https://enesmagnets.pl/en/permanent-magnets/neodymium-sintered/block-magnets/50-x-20-x-20-n35-ndfeb-neodymium-magnet.html

[brandnewb]

Yes Mam,

I just purchased one of those F&P's.

Some time ago I found this 7 phase wiring to reduce coging.
https://www.thebackshed.com/windmill/articles/coglessFP.php

At the end of the article it states special thanks to Bruce! Was that you BruceS by any chance?

pfff a sigh of relieve.

I had the probe on wrong and also the wire ends weren't sanded enough to make the probe latch reliably.

(Attachment Link)

So false alarm thus far. Still no signs of interference.

BTW Mary, if all results are already in of this design, Ed suggested me to take a look at, then how can I be of help giving those a once over?

Is it that perhaps making use of a tesla meter can give some new insights?

Anyways may I please have the link to where this work has been done before me so I can learn and potentially see what Ed meant with how I can be of benefit?

{1}the reason why the waves are rather erratic is most likely because the wires were vibrating as they were banged at while the magnets spun over them.{/1}

With air core coils cogging isn't an issue to worry about! Why iron core has been tried and not used.

For what you are doing get an F&P setup here http://www.randysworkshop.net/order.html and use it to play with your mechanical design, once that is perfected THEN see if you can improve on the alternator part of the equation! The F&P as is will crank out some decent voltage at low RPM, I spun one up by hand and lit a 100 watt 120 volt light bulb! 60RPM = 18 volts! https://www.fieldlines.com/index.php?topic=149388.0 Gear up your design to spin it faster and see better output! Stack 2 or even 3 assemblies if you have the torque and series it for low RPM higher voltage...

Playing with an F&P will teach you about cogging too and how much torque it takes to over come it.

[Bruce S]

At the end of the article it states special thanks to Bruce! Was that you BruceS by any chance?

NOPE! That is a much much smarter Bruce , his moniker was Bruce DownUnder.
He helped champion the rebuild and knowledge of using the F&Ps

[brandnewb]

I know of 11 forms of intelligence Bruce. So I think you are still the smartest Bruce I know of. In most of those categories

But let us not linger on reproduction extremities measuring contests

[JW]

 

With air core coils cogging isn't an issue to worry about!

What is the difference of shorting the phases to shut a mill down.

[brandnewb]

I am also still not confident about it JW.

but my current believe, that I have not been able to demonstrate yet, is that when we use core enhanced coils then their breaking power (the magnetic field they produce at the distance the magnets are at) is greater than while using air core coils.

But now I am running the risk Ed will start losing faith in me as he told me to forget about breaking force.
I am soo torn now between worlds.

I am really so sorry Ed if my next statement will ruffle some feathers And this is in no way a form of disrespect., I just have not enough evidence to just give up on the breaking force concept that @joestru started yet never followed up on.

This is all parallel to the fact that I will build this example you mentioned as I already ordered most components. But in the end of the day we then end up having to compare apples to oranges again we all can not converge on some kind of method to determine how to quantify things.

Let it be heard please that the goal and focus is on a PMA that can kick ass at around 13 seconds per revolution.

Let this be my legacy then. I no longer care if I can build a wind turbine or not. All I care to leave behind is the notion that consistency matters. Let us all agree that the things stated should be repeatable and make sense for future generations yes?

[MagnetJuice]

I should NOT have said forget about Teslas and breaking force.

I should have said:

For now, concentrate on number of turns, resistance, air gap, RPM, volts and amps.

Other things like Teslas, braking force, cogging and terms like that are important, but they will become clearer to you once you have your testing setup and start doing the testing.

quote from brandnewbell:

I just have not enough evidence to just give up on the breaking force concept that @joestue started yet never followed up on."

Now listen, this is very important.

When it comes to the definitions that different people give to technical terms, there could be differences and sometimes misunderstandings.

I want you to define to the best of your ability, what do you mean by breaking force. Please do that for me so I have a better understanding of what you mean.

Ed

[brandnewb]

@SparWeb,
I found your 2006 document at
http://www.jimic.cl/appv/Congreso/PDF/AXIAL_FLUX_HowItWorks.pdf

It describes the Dan Bartmann Axial PMA Ed is refering to, for which I have all 16 magnets in at the moment.

But in the end you write the following
"At 80 RPM, this alternator will produce 50 Volts, unloaded. When connected to a 48V Battery
system, Dan has recorded 600 Watts at 100 RPM. (Roughly 12 Amps). This is actually a
fairly large PMA, suitable for a windmill size of about 17 feet diameter. At higher wind speeds,
the prop turns much faster and he can capture upwards of 3 kiloWatts."

This is in stark contrast to what I am aiming for. Roughly 52V open circuit at 4 RPM.

@MagnetJuice
What I meant with breaking force ability was inspired by Joestru when he mentioned mechanical resistance and MaryB when she mentioned cogging and how much force it takes to overcome it.
The current charge controller I have will short all 3 phases to slow down the turbine. But if the coil/magnet configuration can't produce enough torque/breaking force then not much breaking will happen.
On the same token, if there turbine is charging the battery bank but not much resistance in the turning is being produced then there will be very little wattage available to charge at.

[JW]

Brandnewbie,

There is something you need to take into account. ohms law https://www.fluke.com/en-us/learn/blog/electrical/what-is-ohms-law

This will be key to your calculation's.

Also it relates to your style, you can measure the coils and plug ohms law in and you will understand things differently.

[brandnewb]

hahhah this newbie did find eventually a guide on how to use gravity as a torque/breaking force measuring device.

sweet.

I am going down that path!! to see if I can get anywhere with my original plan.

[JW]

Im not sure if you understand what im saying.

One thing that you have to consider, "resistance" is a dry measurement and "impedance" is what is measured on a live circuit. Again search for an engineering text and read it (book) we may have a way to referrer you a book that will cover the basics. You need to understand common nomenclature. Look into a basic solid state book so you can cover all bases.

[Mary B]

There is a difference between mechanical resistance and electrical resistance BUT the two are tied together in a wind turbine! Electrical resistance can affect cogging... which is mechanical resistance.

Hence JW's suggestion to learn ohms law, and later maybe LC circuit calculations because adding capacitors to each phase can boost the voltage but they need to be tuned to match the frequency and reactance(think of it as ohms for a coil at a certain frequency) of the stator...

Learning basic electronics will really help you a lot!

[JW]

 go on ebay and find this book.  Getting started in electronics  by Forrest Mims

MAKE SURE YOU GET THE GREEN BOOK

[MagnetJuice]

Yea guys, I agree that he should learn at least some basic electricity.

However, I recalled that he said a couple of times before that he has some difficulties learning from reading text.
There is still a lot that can be learned by watching videos and by personal experience.

That is one of the reasons that I recommended to him to build a small alternator.

brandnewb,

If you get the magnets and the steel plates that you ordered, hold on before you start assembling things. It has to be done in a certain order and a certain way.

Ed

[Mary B]

Yea guys, I agree that he should learn at least some basic electricity.

However, I recalled that he said a couple of times before that he has some difficulties learning from reading text.
There is still a lot that can be learned by watching videos and by personal experience.

That is one of the reasons that I recommended to him to build a small alternator.

brandnewb,

If you get the magnets and the steel plates that you ordered, hold on before you start assembling things. It has to be done in a certain order and a certain way.

Ed

That is where the Forest Mims books come in handy, they do small hands on experiments to how the principals being taught... basic equipment needed, multimeter, a breadboard is handy(if it wasn't so dang expensive I could mail him one!), along with a few basic electronic parts that are easy to source, RS Electronics in EU, Digikey has EU offices, Allied has EU offices...

Ohms law is really easy to understand once yu do it hands on! And it is the most used math when dealing with designing a wind turbine.

[brandnewb]

the topic seemed to be headed into the right direction with early contributions of Joestru and MaryB but then got really confusing with images of alternators that clearly will not help both getting an answer to this topic and second to my overall goal of reaching a high voltage at low RPM.

And then to think all I wanted was to stay focussed on a clear goal.

I even reminded about that here in this thread.

I will report back once I have reached my goal.

Thx guys for the input.

Yet I feel we are diverting from the matter at hand.

Please focus solely and only on the matter at hand as outlined below;
 
1) create a bunch of different test coils varying from 0.4mm diam wire size to 1mm diam. and also in shape.

Do make sure that the 0.4mm wire coils are at all times 4 x more winds than the 1mm one. As one can fit only 4 times that wire in the same space of a 1mm one.

2) run various magnet configurations over all variations of the coils at the intended frequency. for single density that would be around 3.8 Hz and for double density that would be double that.

3) record what voltage each coil can produce at said frequencies,

4) hook up an Variable Frequency Drive to the variac at the intended frequency and at the voltage level it would have produced while induced by the magnets spinning.

5) now measure the magnetic field on each coil making sure to also take into account the depth and area it encompasses ( larger is better for breaking ability)


Now what I am looking for is either to hear "sounds like a plan" or "nah this is a bogus plan and I will tell you why"

[MagnetJuice]

QUOTE from MagnetJuice:
After your many requests for help, I'll agree to help you with the design of the alternator for your Phoenix VAWT.

QUOTE from brandnewb:
Thank you Ed,
This means the world to me!

QUOTE from MagnetJuice:
I don't know how successful I will be in getting you back on the road, but I am going to give it a shot.

I failed. 

QUOTE from brandnewb:
Now what I am looking for is either to hear "sounds like a plan" or "nah this is a bogus plan and I will tell you why"

I told you why but somehow you missed it.

QUOTE from brandnewb:
I will report back once I have reached my goal.

I have no idea what your goal is but carry on, and the best of luck.

Ed

[brandnewb]

So preliminary results show that a repelling {1}double density single rotor, dual stator{/1} setup is indeed a dead end and quite frankly a bit of a foolhardy idea to begin with .
I can only get a few winds in a coil at best before the coil gets so tall (2 maybe 3 layers only) the field already drops to unusable values.
So finally I can close the books on that concept.

Now it is still the question "to stack coils or not to stack coils".
But I am leaning against it because although I have not yet demonstrated it I am not sure what the magnetic field in the coils will do when they are tilted diagonally slightly. I can only imagine it will not benefit the interaction between that field and the magnets.

Another, perhaps far more important reason not to stack coils. One that I have demonstrated already is that with having coils stack then heat dissipation rates drop to near zero. Ok truth be told I have not really sunk my teeth into that problem yet to see if I can fix that.

Anyway. I can generate around 1.17vAC at around 3.8Hz with a single stacked coil pair when each coil in that pair has 50 winds (I am ignoring coil{2}wire{/2} size for now).
And theoretically we can have 48 of those stacked pairs per phase making for around 56vAC at 3.8Hz. In practise I will need some empty coil slots at every stator segment else not be able to (de)install it in a modular fashion.

For traditionally spaced coils we can have 24 coils per phase. But the good thing about the coil shape in this scenario is that it can be wider. Maybe even enough more wide to compensate for the extra winds needed to be able to reach around 2.1vAC per coil at 3.8Hz.
And then of course all the added benefit mentioned earlier.

reporting back once I managed to figure out how much winds that is.

[JW]

Here check this out don't be afraid of the link...

   Maxitronix 200 in 1 Electronic Project Lab - Educational Fun Basic Electronics


https://www.ebay.com/itm/325986261679?chn=ps&_trkparms=ispr%3D1&amdata=enc%3A1w69pfJeBT_G2HVVkGUhmcw63&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=325986261679&targetid=1585159290171&device=c&mktype=pla&googleloc=9013362&poi=&campaignid=19894961968&mkgroupid=148855406073&rlsatarget=aud-1317302328205:pla-1585159290171&abcId=9307911&merchantid=603800276&gad_source=1&gclid=EAIaIQobChMIg6Obms26hAMVUBmtBh0skwz4EAQYBCABEgJ0A_D_BwE

Before there was Forest Mims

The projects will at least teach you how to read a schematic diagrams

[brandnewb]

So gang. first most please accept my humble apologies for being stubborn.

It is one of those self defense mechanisms that kick in when information gets too difficult for me to process in a, for me, suitable time frame so I just default back to where I was.

It is nothing personal nor will it ever be.

So here is my update thus far.

!!If at any time someone feels I should demonstrate because something does not make sense then please do so to signal that. Because then I will and maybe we find I blundered again.
If it all makes sense to you then I am also content to just go with this flow!!

Context: 300mm radius ID of magnets spaced at a 3.75 degree interval.
Considering non stacked (traditionally spaced with an air gap of around 20mm (4 times that of the magnet thickness) 24 coils per phase) coils even though wider of nature than stacked coils will need about 280 winds to end up in the 2.something volts sphere.
While when stacking coils (48 per phase) in this context only needs coils to be 50 winds to end up in the 1.something sphere of volts.

And I think I can explain why.
You see magnetic fields when induced by electromagnets (the coils) they do interfere with each other. But then in a good way. In where overlapping phases compound.
And here comes the kicker!! The adjacent pole in the same phase does not counteract the other. Not al all!

I just love magnetic fields soo much If only I understood them

Overmore the field around said coils is non biased for direction. It is a sphere so that means that my earlier worry of having tilted coils would harm the interaction with the magnets seems debunked.
But I know for sure once I start the torque tests. Now I am still in the finding out what configuration actually stands a chance of getting where I need to get.

Anyway all this has set me back on track with the original plan to go for a large diameter. a 300mm ID {1}inner radius{/1}was just to see. Now I have seen and I can tell. Nah that diameter will never work for my goals of having 52vAC at 3.7Hz (yes it is 3.7Hz not 3.8Hz like I have been mentioning earlier)

Also Ed, You know that I love you so that is why I have not send back the 16 magnets yet. I will keep them ready and waiting so that later on once I have some real life data I can setup a gear ratio to have this suggested setup spin around 20 times faster than what I am making. Just to compare results.
In case my configuration lacks behind then we have a clear indication why not to go with a direct drive for a low RPM VAWT.

I have more to say but no time to write it now.

[brandnewb]

So I have some time again now.

I am back again at an IR (inner radius) of 600mm because that will roughly double the velocity at which the magnets spin over the coils and roughly double the area we get for the coil wires to play in.

But to my shock I was unable to measure/demonstrate the expected effect.
You see I tried using a 25 winds coil at the original (600mm IR, 3.75 interval, traditional, dual rotor, single stator) and got crap results. Not at all what I expected.

So now I need to figure out what it is I am doing wrong. And yes I did check the proper connection to the oscope 

{1}I would love it if anyone would just blurp out any random thought of what can be going on here and/or how to zero in on a possible root cause.{/1}
{2}Also the most important revelation to me is that one should not be looking for a straight line in magnetic fields in between rotors. Some dispersion adjacent wise will actually help for the coil shapes I am considering.{/2}

[MagnetJuice]

Also Ed, You know that I love you so that is why I have not send back the 16 magnets yet.

That's the second time that someone told me that they love me today. Cool, that's a good way to start my weekend. 

Hz is cycles per second. 3.7 cycles, or magnets passes over the coils in 1 second equals 222 RPM.

Is that how fast you want the turbine to spin?

I am sure that you mean 3.7 RPM and not 3.7 Hz. Right?

Ed

[brandnewb]

@MaryB,

I just got refunded my purchase of the F&P

Randy tells me that shipping is an additional 102 USD

I would have loved to play around with something like that. And indeed the stacking suggestion you made really is attractive to me.

Anyhow let's look forwards!

[brandnewb]

I am glad I made your weekend brother. Love is indeed the intend.

So I actually mean Hz in voltage waveform. Like on the oscope pictures I share from time to time.

Given there are 96 magnets on a single rotor disk that rotate fully every 12.something {1}closer to the 13 mark{/1} seconds that equates to around 4 RPM and around 3.7Hz of full voltage waveform.

I realize it is a bold goal. I think I can get there.

Now I am ok if we forget about magnets to watts. Let us focus on how to quantify things this early in the prototyping stage yes?

All I care about is to be able to say something that people will believe. And also not to just build and build only to find I missed something crucial ending up with an alternator that does next to nothing.

Also Ed, You know that I love you so that is why I have not send back the 16 magnets yet.

That's the second time that someone told me that they love me today. Cool, that's a good way to start my weekend. 

Hz is cycles per second. 3.7 cycles, or magnets passes over the coils in 1 second equals 222 RPM.

Is that how fast you want the turbine to spin?

I am sure that you mean 3.7 RPM and not 3.7 Hz. Right?

Ed

[Mary B]

@MaryB,

I just got refunded my purchase of the F&P

Randy tells me that shipping is an additional 102 USD

I would have loved to play around with something like that. And indeed the stacking suggestion you made really is attractive to me.

Anyhow let's look forwards!

I know you can find one in EU... heck go to an appliance store and ask if you can raid a bad washing machine for parts. They were widely used there before coming to the USA.

Another possible choice is an ECM motor from a heating/cooling system. Used to drive the big squirrel cage fan on forced air systems.

[brandnewb]

I have a washing machine currently on sale through a second hand market channel.

In case the final offer is not convincing then I will rip apart this machine. carefully though