First PMA With Lackluster Results

[BBT723]

So I made my first PMA with high hopes.  I used (12) 1.26”x.25” N42 magnets on my rotor and tried a single (9) loop 22g serpentine coil with a thickness of .25” at 50 turns. My RPM on my testing jig was around 1000. The air gap was close to .125”.

I ran the testing jig aiming to see 12 volts on my multimeter and only got around 2 at best.  I’m clearly not well versed enough to deduce my errors.  My main assumption is that I either poorly made the coil or I used the wrong wiring.  Attached is an image of the coil.

Any insight would be greatly appreciated from you guys.  Thanks in advance!

[Bruce S]

First, Those look like a very nice winding!!
However, it also looks like it is one continuous winding.
I'm attaching a much older post but the pictures that are in it will give you a good idea of what's involved.
https://www.fieldlines.com/index.php?topic=148633.0

Since the wire looks very well wound you can probably repurpose it into 9 separate coils.
Give us a bit more information and we can help you a little further. What beside 12Vs are you aiming for and how to are you going to spin the mags?

BTW: Welcome aboard.

Cheers
Bruce S

[Mary B]

yup that is a continuous winding... and the way it is done it is not going to do much at all.. if your intention was a continuous winding wind a coil then move to your next space and wind the next... I have never played with a continuous winding so don't know if you need t reverse each coils direction...

[Adriaan Kragten]

This is a very strange winding. I see a continuous serpentine wound coil. So this is a 1-phase winding. It has nine loops and so it needs an armature with nine or eighteen poles. Nine poles isn't possible as the number of armature poles must be even! But for eighteen poles, the distance in between the inwards and the outwards radial part of the loop must be the same which isn't the case. So the winding is far from optimal for an 18-pole armature. So don't make a winding if you have no proper idea of the armature. You can make a winding with nine separate coils for a 12-pole, 3-phase generator but only if the coils of the three phases are separated from each other.

Car generators often have 12 poles and a serpentine winding but with a separate serpentine for each of the phases. The winding is first made as one big round coil and next one uses a special tool to transform it into a serpentine. Mounting of a serpentine in the stator stamping is easier than mounting of separate coils.

[Bruce S]

With Windstuffnow's great assistance, (https://www.windstuffnow.com/) I did do a few small Wave-Windings. Worked out pretty well.
Like both Mary B and Adriaan pointed out, this is one continuous winding.

IF you're really stuck, come back with a few ideas of what you're trying to accomplish [Even if it's just to learn (which is super cool too!)].
We should be able to help , even if it's just pointing to a really good post where the questions are already answered with some cool pics.

Cheers
Bruce S

[BBT723]

Thanks everyone for your responses.  I initially planned on using (9) individual coils but I came across a youtube video showcasing the serpentine method which I used.  Based on your comments, the easiest solution would be to just do the (9) individual coils.  While its' sad to say, I watched the video and ran with it as it looks easier and supposedly worked the same as the (9) coils.

My ultimate goal was to generate around 100 watts.  I did some limited research and determined that using a single rotor housing (12) N42 magnets and a stator housing (9) coils above 480 RPM could get me close to the 100 watt goal.  I did decide when I ordered the wiring to get a wide range of sizes, from 14 to 26 gauge.  As I stated before, I used 22 gauge thinking it would suffice.  Would it suit me better to go with a higher or lower gage?

Sorry in advance for my ineptitude on the subject! 

[Adriaan Kragten]

If you want to make an axial flux PM-generator with no iron in the coils, you can better use a 3-phase winding than a 1-phase winding for two reasons.

The first reason is, that if you rectify a 1-phase current, you get a very fluctuating DC current and so also a fluctuating torque. Batteries don't like a very fluctuating current especially if they are loaded simultaneously with the charging because this results in fast charging and recharging. If you rectify a 3-phase current, there is only a small fluctuation on the DC current. Information about different ways of rectification is given in my public report KD 340.

The second reason is that you can get 50 % more copper in a 1-layer, 3-phase winding than in a 1-layer, 1-phase winding. Information about a 3-phase winding of an 8-pole axial flux generator is given in chapter 9 of my public report KD 341. Once you understand an 8-pole, 3-phase generator, it is easy to understand a 12-pole, a 16-pope or a 20-pole generator. The pole number must be dividable by four if you want to use a 1-layer winding. A 1-layer winding means that all coils are lying in one layer and so there are no crossing coil heads. All my public KD-reports can be copied for free from my website: www.kdwindturbines.nl at the menu KD-reports.

[Bruce S]

Thanks everyone for your responses.  I initially planned on using (9) individual coils but I came across a youtube video showcasing the serpentine method which I used.  Based on your comments, the easiest solution would be to just do the (9) individual coils.  While its' sad to say, I watched the video and ran with it as it looks easier and supposedly worked the same as the (9) coils.

My ultimate goal was to generate around 100 watts.  I did some limited research and determined that using a single rotor housing (12) N42 magnets and a stator housing (9) coils above 480 RPM could get me close to the 100 watt goal.  I did decide when I ordered the wiring to get a wide range of sizes, from 14 to 26 gauge.  As I stated before, I used 22 gauge thinking it would suffice.  Would it suit me better to go with a higher or lower gage?

Sorry in advance for my ineptitude on the subject!

I for one would like to have a LONG look at the U-tube vid you speak of. It would be "interesting"    
Do stick around and do a bit reading, your winding looks nice, therefore you should get the hang of winding coils with little prob.

Bruce S

[JW]

I always find this stuff interesting. Have  I read about coil canceling ? WYE or Delta series or parallel. I don't have my workstation working with a monitor so I would make a longer post. Ohya I wanted to reply t0 the magnetic fields post and say magnetic fields are not lienor.

[BBT723]

Thanks again guys.  I’ll search the forum and find additional pertinent info!

FYI I couldn’t post the link to the video but go on YouTube and search “ (2) How to build a homemade P.M.A generator serpentine stator for my new V.A.W.T” by Aceman307.  That’s what I followed!

[JW]

Ya I think we set it so that you would need 20 posts before you can post a link or picture. I have worked real hard so that images hosted by the forum are archived.

[Bruce S]

OKAY!
Now that I'm watching what this guy did, it's pretty much a take off of Ed's original "WAVE" winding.

https://www.windstuffnow.com/main/3phase_turbine_kit.htm.

From what I can tell in your picture you forgot to offset for the 3-phases  . OR you did not complete all 3 phases. If you take a look at his picture of the Stator at about 2:42 in the VID, you can just see them offset and he explains that they are offset by about 120 degrees.

This make a big difference, even then he only got about 4.5V output.
I'm skeptical of his output as he only states that the voltage is.

Hope this helps

BTW: What was your output from the current setup?

Bruce S

[BBT723]

I got just above 2 volts.

Now that the smart plan is to do a 3-phase 9 coil set up, anybody got a tip on determining the voltage when you have 3 wires and my multimeter has 2 connection points?  The reason I ask, from what limited knowledge I have, is that I need to know that before I can get the appropriate rectifier, right? Or is there some simpler of determining the voltage?

[JW]

If your checking  the database use keyword "wire in hand"

[electrondady1]

your wave winding is completely wrong.
i am assuming the large loops of copper are meant to circle your magnets
the small loops of copper on the inside  should not exist

starting from scratch. you have  a small  length of copper  you will use for making  the electrical connections .
 now wind the wire half way  around the inside of  first mag and then half way around the second magnet on the outside
now the wire travels back to the inside of the 3rd magnet  and then back outside of the 4th magnet
this continues around  and around

without knowing the dimensions of your magnets or the spacing between them,
  what is required it that one leg of the loop is  just beginning to cross a magnet
 while the other side of the loop is just beginning to cross the second magnet.
this will produce single phase electricity

you mention the numbers 12 and 9  which is the ratio of magnets and coils used for three phase output.
in order to produce 3 phase electricity you will need to create 2 more such wave windings off set from the first

 i hope this helps



 

[BBT723]

your wave winding is completely wrong.
i am assuming the large loops of copper are meant to circle your magnets
the small loops of copper on the inside  should not exist

starting from scratch. you have  a small  length of copper  you will use for making  the electrical connections .
 now wind the wire half way  around the inside of  first mag and then half way around the second magnet on the outside
now the wire travels back to the inside of the 3rd magnet  and then back outside of the 4th magnet
this continues around  and around

without knowing the dimensions of your magnets or the spacing between them,
  what is required it that one leg of the loop is  just beginning to cross a magnet
 while the other side of the loop is just beginning to cross the second magnet.
this will produce single phase electricity

you mention the numbers 12 and 9  which is the ratio of magnets and coils used for three phase output.
in order to produce 3 phase electricity you will need to create 2 more such wave windings off set from the first

 i hope this helps

My magnets are 1.25" so I guess I'll need the individual coils to have an ID of 1.25" and with the thickness of the coil legs being .25" (or should it be .5"), the OD will be 1.75".  Based on a sketch I just made, it should satisfy the crossing you mentioned.  Right?

[MattM]

Nothing wrong with short pitch windings if they align to poles.

The wires are not aligned properly to the fields you're making.  This guy might help you see what is happening.

https://www.youtube.com/watch?v=rTsRSTzeqaM

[electrondady1]

here is a video  that shows a wave winding stator being produced your coil jig is much better than this fellows but it shows how the copper wire fits around the magnets 

[Adriaan Kragten]

here is a video  that shows a wave winding stator being produced your coil jig is much better than this fellows but it shows how the copper wire fits around the magnets 

The serpentine winding in this photo is a 1-phase winding for a 12-pole armature. The voltage is only generated for the part of the coil for which it is in between the magnets. So these are the twelve radial parts of the coil. The coil has six radial parts where the current flows inwards and six radial parts where the current flows outwards. So if a north pole is opposite to the radial part where the current flows inwards, a south pole is opposite to the radial part where the current flows outwards. This means that the voltage generated in both parts of the coil are strengthening each other and this results in the maximum voltage for a certain number of turns per coil and a certain rotational peed. The optimum shape of the coil is such that the radial parts of the coil are straight and exactly radial. So this means that there is an angle of 30° in between the radial parts of the coil for a 12-pole generator.

[MattM]

He can still use his 9 'coils' with 8, 16, 24, or 32 magnets aligned with 8 outer short pitches.  The 9th short pitch would not have a magnet.  He can probably realistically do the same with the inner short pitches.  (The term, short pitch, is used to describe a coil that forms partial circles.)  He can run a counterweight in the 9th position to balance it out.  Why throw out what you already got?

[MattM]

https://www.youtube.com/watch?v=TWjiBuVQy84

[electrondady1]

BBT723, in my opinion about 30% of the copper in your jig will not be crossing any magnets so is only adding resistance.
 if it were my project i would rewind  without using those innermost loops.

[MattM]

I see both the inner- and outermost loops being the issue.  The right hand rule implies he would want all of his wires 90⁰ to the magnetic fields.  The electrical potential nosedives to zero as you reach parallel to these magnetic lines.  All of those lines need to sit in a line pointing as close as possible to dead center of the stator.  This should lead to more of a teardrop shape.

[electrondady1]

OK,  i just reread the thread and i think you right in winding 9 conventional coils and leaving the wave winding altogether . you haven't mentioned it but is there a second rotor and set of mags to create a 3 phase dual rotor axial flux alternator?



 

[BBT723]

Update: I modified the loop layout to have 6 loops and the results were surprisingly good! I got around 7.5-10 volts on average around 480 RPMs!  Attached is a pic of the revised coil and volt readings on my tester. 

My next plan is to make 2 more for a 3-phase system and place another magnet rotor on the other side.

I’ll probably discover the answer before I get a response, but are the magnets on the top and bottom rotor pole symmetrical?  Say one magnet’s face towards the coil on the top rotor is N, does the magnet directly below it need to be N as well?

[MattM]

Opposing



See https://www.animations.physics.unsw.edu.au/jw/electricmotors_staticimages.html

[MagnetJuice]

I had this image ready to post when Matt posted. Here it is anyways.



How are you planning on laying the coils for the other two phases so they are 120 degrees out of phase with the first coil?

Ed

[Bruce S]

How are you planning on laying the coils for the other two phases so they are 120 degrees out of phase with the first coil?

Ed

Ed;
I think if he does it like Ed of Windstuffnow shows on his pdf, he should be able to skip one of those round thingy's and start the next wind, then skipping the next round thingy's and to start his 3rd one.
Ed's PDF is open for free d'load so I'll attach it to this reply. Around page 5 is where the explanation shows pics.

Ed used slots , but the hole/pole thingy's should work about the same.

 3phasekit.pdf (490.95 kB - downloaded 26 times.)
Hope this helps

[BBT723]

Based on my current design, I can't get the 3 serpentine coils situated to meet the 120 degree requirement.  Guess I'm going back to individual coils after all!  Thanks guys for clarifying the pole alignment!

[Bruce S]

BBT723;
I was hoping you would continue down the wave windings road.
I wouldn't tear this down just yet, you got a nice 7+ volts and who says you have to be perfectly 120 shifted.
Since you have 12 [poles] the shift will be different. I couldn't see the magnets arranged, but , you could still make use of this current arrangement.

BTW: Where you able to get a current measurement?

Cheers
 Bruce S

 

[joestue]

you can keep your winding but you might modify the coil former to get the voltage higher.

anyhow make 2 more copies of the coil you have, fit them together and then press them between two disks and the end turns will conform to make room for each other.

[MagnetJuice]

BTT, forget what I said about 120 degrees. It is relevant, but it could confuse things a bit at this time. Those coils should work.

Those 12 magnets on one rotor are capable of producing over 200 watts. It would be safe to use 18 Ga. wire for the final alternator.

Those magnets are not very thick, so you need to make the coils as thin as practically possible to get the copper close to the flux.

Or you can go with 12 magnets and 9 individual coils. I think is easier.
 
You are doing great; those coils look good.

Ed

[Adriaan Kragten]

Based on my current design, I can't get the 3 serpentine coils situated to meet the 120 degree requirement.  Guess I'm going back to individual coils after all!  Thanks guys for clarifying the pole alignment!

Yes, a serpentine winding is good if you have only 1 phase but for three phases you will get three layers on top of each other. and this gives crossing coil heads which makes the winding rather thick. If you want a 1-layer, 3-phase winding for an axial flux generator, you can better make separate coils and take a total coil number which is 3/4 of the number of armature poles.