Modified AC Generator but 0 AC Voltage

shortbus

Joined Sep 30, 2009
7,078
Getting there! Look at some of the things shown in this Google about how stator's are wound. It's the pattern and number of raps that give the volts, and the gauge of wire that determines amps. I'm kind of doubting you actually have 3 phases though, and it would be better if your goal is to make DC to go with a single phase.
https://www.google.com/search?client=firefox-b-1-d&ei=cd_JXceiCNHUtQXZ9rSIAQ&q=alternator+winding+design&oq=stator+winding+in+an+alternator&gs_l=psy-ab.1.1.0i71l8.0.0..20400...0.2..0.0.0.......0......gws-wiz.ZXXl73DGQa8
 

cmartinez

Joined Jan 17, 2007
6,593
I'm thinking that a nice experiment to try would be to place another non-rotating steel drum inside your assembly, to help concentrate the magnet's field lines that cut through the windings as the magnets rotate ... see if there's a change in behavior ... that way you'll corroborate if said Halbach array is as good as it's supposed to be.
 

Thread Starter

sourceless

Joined Oct 28, 2019
26
Yes, def I need thinner wire so that I can get more volts and make better use of the tiny pockets.

Just put the second phase. This time I was lazy and tried a different approach. Used a frying pan to make the whole coil and then zig zag it on to the stator. Much faster but there was a bit left over. It was not the right frying pan :)

I've put the 2 phases in series and I get 2V AC now, and I finally light the LED.

I don't have a meter to measure the variable amps so I will have to wait till I do a rectifier ( didn't find a tiny rectifier for 3 phase on aliexpress). But when I spin it by hand and then short circuit I can feel the break. Rotor is kinda heavy with the 48 magnets and has a good momentum so I really hope it can do some watts.

Final destination is hooking it up to this so it lights up some diodes:
 

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Thread Starter

sourceless

Joined Oct 28, 2019
26
Look at some of the things shown in this Google about how stator's are wound.
Will do, up until now serpentine coil seems the easiest to play around.

I'm thinking that a nice experiment to try would be to place another non-rotating steel drum
Where? on the inside of the stator just behind the coils?
Somewhere in your thread I read that the axial's generator metal disk(without magnets) should be rotating together with the magnets on the other side.
Or is tha idea this metal drum to act like the statot laminations?
 

Thread Starter

sourceless

Joined Oct 28, 2019
26
Just setup a delta connection with the 3 phases. (end of one coil connects to the start of the next one)
Now the generator has load all the time cause it's essentially a short circuit.
Is that normal? Am I missing something? Shouldn't it be freewheeling.
 

shortbus

Joined Sep 30, 2009
7,078
Now the generator has load all the time cause it's essentially a short circuit.
Is that normal?
Any short circuit will be seen as a load, and one that is higher than any driven load.

What my earlier Google post should have shown you is that alternator winding's are similar to induction motor winding's, they are what is called a "distributed winding". That means that each winding takes advantage of many magnetic poles at one time.

If just doing this to try different things is your goal that's fine. But if your really wanting to get somewhere without making a lot of starts and failures, you should do some research on how things work. Don't know how old you are, but there is much more information at our finger tips today than when I was young, seems like a shame not to take advantage of it.:)
 

Thread Starter

sourceless

Joined Oct 28, 2019
26
So the delta connection is not freewheeling?

Yep, doing lots of research in the spare time but questions don't get fewer :D.

Thanks for your inputs, they def helped me speed up things.
 

Thread Starter

sourceless

Joined Oct 28, 2019
26
Inside the stator, and rotating in sync with the magnets.
It would be too hard to do. Maybe in an axial one.

just made a 3 phase rectifier and tested latest version:
- 48 magnets on the outside of the coil, halbach array
- 3 serpentine coils wound 12 times each ( 1 serpentine has 24 turns, corresponding to 12 coils???) - 0.5mm cable
- 3 phase AC
with a star connection:

1V max
0.1 A max
separately measured with hand-cranking, don't have two meters.

so maybe 0.05 watts? :eek:
pretty disappointing. I was hoping for at least 5-10 watts.
Unfortunately I don't have proto-pasta to test with it.
If this guy has done 60-70% efficiency must be a promising test to do. https://www.makesea.com/brushless-motor
Is the efficiency two way for a motor & generator?


Tested the initial motor that I downloaded from thingiverse.
- 32 magnets on the inside of the coil, halbach array
- 2 serpentine coils wound 25 times each (each serpentine has 16 turns corresponding to something like 8 coils???) - 0.5mm cable
- 2 phase AC
star connection:
2.5V max
0.1A max

The original generator has more copper but mine has bigger radius.
Still, it looks like my "optimisations" are with a negative value :)
 
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cmartinez

Joined Jan 17, 2007
6,593
pretty disappointing. I was hoping for at least 5-10 watts.
That's why I was hoping you could place that steel drum to see if increasing its efficiency was possible. And on the other hand, 5 to 10 watts by hand cranking something, especially without a belt-pulley-crankshaft assembly is a bit harder than you might think.
 

shortbus

Joined Sep 30, 2009
7,078
Your coils vs magnets need more explanation. Not remembering the geometry off the top of my head, there is a much needed number of coils to magnet ratio. I have no idea how it works out with Halbach's though since the span of the magnets involved is much larger than a normal alternator. Like in most car alternators there are 12 "claws" on the rotor and 3 distributed coils in the stator. That ratio is something for you to look for in Google, and pretty sure it would be mentioned somewhere in the last Google link I gave you on stator design.
 

Thread Starter

sourceless

Joined Oct 28, 2019
26
Your coils vs magnets need more explanation.
I copied the design from here: https://www.thingiverse.com/thing:1693579
Where for each 2 poles(4 magnets) you have 2 coils (4 vertical slots), I added a 3rd coil by making sure that:
two of the slots of a single coil are still facing different poles at the same time.
Maybe when "magnets poles = coils" it works ok for a two phase. But for a 3 phase 4/3 ratio is the most common.
So now when I'm having 3 phases with equal magnets and coils means they overlap a bit, right?
What happens after the rectifier when you have 2 phases to overlap with a different Voltage and same polarity? Is it lost, is it compounded in some kind of way? (if load can't make enough voltage sag to the lower one, nothing is won from it?)
Will most probably have to fix the magnet / coil ratio.

Maybe I will try cmartinez's suggestion to straighten up the magnetic flux.
 
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Thread Starter

sourceless

Joined Oct 28, 2019
26
I'm writing from the future. Tried the metal rotor - didn't work. Have to debug - thickness of metal, material, air-gap.

Used a cap from something like a tin can(9 mm on the side, has a similar top surface also - don't know if this would spoil the flux way). Magnets stick to it well but it's very thin. Did a space inside the stator and made a rotor to plug it in. Unfortunately it's about 8 mm away from the magnets so it might not be working.

Did 1 coil with about 25 turns 0.5mm - 12 coils.
Again 1 V.

It's not in all equal case but seems like in the same ball park. The suckers ball park.
 

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shortbus

Joined Sep 30, 2009
7,078
Is that your turbine? If it is it's cool that you went with a modified Darrieus type. If I was younger and going to do this that is what I would use, but wouldn't make it vertical. Putting one horizontal on the ridge of a roof would be my way of doing it. That would also force the wind from the surface of the roof to make it turn at lower wind speeds.

I don't think your going to get much extra from using the iron infused PLA. The magnetics isn't going to be the same as real steel/iron. The iron PLA is going to be more like a ferromagnetic core, or ferrite like used in high frequency magnetics. That is why you don't see any ferromagnetic cored electromagnets. Ferromagnetics are used where you don't want saturation, and that is what is needed for a generator.
 

Thread Starter

sourceless

Joined Oct 28, 2019
26
I downloaded it from thingiverse. Very hypnotising to watch. Maybe should play with the colours. It's a bit wobbly at low rpm but when it reaches very high rpm in high winds, it stabilises. Pretty interesting!

Good idea about the rooftop, I have only a balcony. While usually it's a bad idea to harvest wind near buildings because the wind flow is slower and not "clean", it's fun :). It's creeping out the neighbours with a red diode when spun.

Thanks for the point of the ferromagnetics. A bit confused if this guy is reaching 60% efficiency for a motor, isn't it 60% efficiency on the reverse path? Just found where he states "And we can estimate that the magnetic PLA amplifies the magnetic field by a factor around 1.4"

Shall I just go for an axial one with two metal plates? Maybe more diy friendly.
 

shortbus

Joined Sep 30, 2009
7,078
I got the idea for a horizontal one while watching how snow was blowing off of my barn/shop roof. It was moving faster there than on any flat surface.

I still don't understand the desire to create 3 phase to light a LED. The more changes in form of the power you make the more loses you get. A simple bridge rectifier will give a loss of ~1.4 amps when making AC into DC, from the 2 diode drops involved. Then when you do the 3 PH rectifier you get a drop of ~4.2, due to the 6 didoes involved. https://en.wikipedia.org/wiki/Single-phase_generator They say generator in the title, but it really is about alternators making AC.

And taking some ones word about a type of PLA with minimal iron powder in it, minimal because it wouldn't bond if it had too much in it. Most people posting things to Youtube or Thingverse or other such sites, don't reall understand what they are telling you, so it's kind of the old saying of "buyer beware". Where they are selling people a load of BS.
 

Thread Starter

sourceless

Joined Oct 28, 2019
26
I still don't understand the desire to create 3 phase to light a LED.
I'm staying too much on the computer and am seeking engineering leisure activities off it - efficiency is not a must at this point. Something to 3d print and assemble. Built 2 racing drones (that was pretty challenging from scratch). Went for 3 phase as this was the first thing google returned I think. And because there was this 2phase generator on thingiverse.

The more changes in form of the power you make the more loses you get.
Completely aware of that but I'd like to spend more time off the laptop. Otherwise I'd need an extensive research for the better pathway again on the computer. Tried to check out the BLDC generator but seems more complicated.

taking some ones word on the internet
You got me here. It seems to me that the the man uses decent scientific approaches.
 
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