Axial Flux 3 Phase Delta / Wye Wiring (Rectified)

[arc]

Attached Drawings:
1) Wiring (Star and Delta) with Bridge Rectifiers
2)Stator Coil
Note: I reduced the jpg size so I hope there is enough detail left to see what's going on.

I'm working on a (very small) single rotor, Axial Flux, 3 phase wind turbine.
Rotor diameter is approx. 7 inches with 20 ea. round neos 3/4" dia. x 1/4" thick. (Rotor backing plate is a go-cart sprocket so about 1/8" thick).
Stator will have 15 Coils, each with 70 turns of (high temp) 20AWG magnet wire.
Coils will be trapezoidal with an I.D. of approx. 3/4" and O.D. of 1-1/2" (width and height) and 1/4" thick.
I'll make the stator with 6 connection points so I can play with star or delta wiring (since I have little idea of what voltage it will produce).
I chose 70 turns on the coils since that's about what room I have. As for the 20 ga. wire, that's just what I have on hand.

I don't expect much output (of course) due to it's overall size and in particular the magnet size, it's just a fun little project that I hope will light some deck lights (LED's).
If I can get 14 volts @ 70-120 RPM I'll probably just clamp it to a 9Ah gel cell without any controller circuit then power the LED's from that.
If not, I'll think of something.
Rotor is built but I haven't tested a coil yet to see what kind of output I might get out of this.
I think my coil size should be fairly closely matched to magnet size and spacing and will keep the air gap to a minimum so hopefully I can squeeze something out of these tiny little magnets.
I've got some of those (Ametek type, roughly 60" dia.) narrow tip blades left over from an old project so I thought I'd see if they would get this little unit spinning.

Was hoping Flux or others might look over the general wiring to be sure I've got things wired right. (Especially the Rectifiers).s

As always, any thoughts or comments are most welcome.

Thanks
Arc out

[JW]

Looks good, there is a color schematic Im going to insert here will be a good reference for those looking for this wiring information



JW

[Flux]

Looks fine except for the delta links. For delta you need to link start to finish.

I am struggling to trace the lines on the drawing but it looks as though the phases are A to X , B to y and C to Z ( not the same as on the coloured diagram from JW.)

If I am right then link AZ. BX and CY and these links become your rectifier leads.

Flux

[arc]

Thanks JW and Flux,

Attached:
Star Dawing
Star Connection
Delta Drawing
Delta Connection

I'm hoping that these pics are a little easier to see what's going on with my connections.
(This image manipulation is tricky business for me ... but I'm determined). 

Flux - Check out the Delta Drawing to see if my connections make sense now.

Thanks,
Arc out

[arc]

My Letter assignment on the Delta Drawing was a little ambiguous so here it is, corrected.
 Flux, you are 100% correct, "the phases are A to X , B to Y and C to Z".

Connections between terminals here should be AB, CX, YZ to form the Delta. (As Shown below).
Any predictions on achieving a usable voltage with this setup?


Well, I got two coils wound and they are turning out the right size/shape so I just need to keep going.
Dang that Super Glue, no matter how hard I try, I still get some on my fingertips.
I picked up some fiberglass cloth and a quart of resin so I can make the stator.
Plan is to make the stator about 5/16" thick and have 3 ears to allow room for mounting holes.

Just a Side Note for those who haven't wound coils before:
To get nicely formed coils it really helps to do some prep work. Make a coil winder out of two plywood discs ~4" diameter with hole drilled thru the center.
Make a template the thickness and shape of the coil's center opening. This template is sandwiched between the two discs and a long bolt placed thru all.
A washer and nut secures discs together.
A screw with a short tube (or straw) makes a handy crank handle, the long bolt will act as your axle.
Using an old candle, Wax all surfaces that will make contact with the coil, the Super Glue won't stick to it.
I made two "V's" in each disc so I could lay some electrical tape (sticky side up) in the "V" to wrap the coil when finished winding.
The "V's" also allow you to add a little supper glue every 3-4 layers of winds to keep the coil formed nicely.

Place your coil wire on an axle (dowel) perpendicular to the coil winder and let it roll off the spool rather than spiral off one end.
I like to have some tension on the spool so it's easier to wind nice layers as I go.

Arc out

[just-doug]

in my experiance with small magnets they just get buy with two mag rotors.yours if you stick to only one rotor ,might just be junk,if you couldnt get enough turns in the stator.just a thought.good luck and keep posting.

[Flux]

arc

Your delta drawing is still wrong, think of it this way, if your star rectifier connections are X. Y and Z then these will also be delta leads. You need the finishes A B & C to be in sequence to complete the ring. Start of one phase connects to the finsh  of the next to become one line connection.

If you follow that sequency you will see that your blue phase is reversed. A and B can't be joined. Phase 1 will be AY and phase 3 wil be BZ.

Flux

[arc]

Ok, I see what you mean Flux, glad I ran this by you or I would have had major problems testing down the road.
I fixed my drawings to reflect the connections as you suggest.
X,Yand Z now connect just as with a Star configuration and A,B and C connect with Y,Z and X respectively.
(In other words both go around the Delta Clockwise)

Thanks for your help Flux!
I think I've got it now.
Hope my previous drawings don't throw anyone off in the future.

Attached:
(Corrected Delta Wiring Connections)

Delta Drawing
Delta Terminal Connections

[oneirondreamer]

I tried a single sided array, and found that my volts produced almost doubled by using an iron plate behind the coils.   My setup was sophisticated enough at the time to measure efficiency, to see how much energy was being lost to eddy currents in the backing plate.

[arc]

Ran out of magnet wire last night and I've only got 11 out of 15 coils wound ...
... so I ordered some more 20AWG and while I was at it ordered 20 more magnets (same as the ones I have noted above).

If I can find another steel plate (rather not use a saw blade but will if nothing else) I'll just sandwich the stator between two rotors and, with a little luck, perhaps I can get within range of my desired 12-14 volts.

I think you're right Oneirondreamer, I need to really channel those flux lines to even have a chance to make usable voltage with these small magnets.

Arc out

[arc]

Hi Just-doug,

Didn't mean to ignore you ...
... as you can see from my post above I'm going to add a second rotor.
I may test with one rotor first, just to see what kind of difference it makes.
I have little doubt that it will make quite an improvement.

I'll need to revise my bearings and stator mounting (beef things up some and make allowances for second rotor) but I'm sure it will be worth it in the long run.
I still am keeping my expectations in check and don't know if I can get much voltage in low winds but we shall see.

Arc out

[arc]

Update:
Second rotor has the 3/4" dia. magnets epoxied to another go-kart sprocket which is the same as the first rotor.
Axle and bearings are now set up on the main backing plate and I picked up some bots, nuts etc to get everything spaced correctly and adjustable.
As soon as I get set up with a stable arm for testing coils I'll be making some progress.
Still not sure (until I get some testing done) whether or not I'll achieve my goal of 14 VDC with enough amperage to trickle charge a 12V battery.

I'll keep you posted on any testing results and further progress on the build.

arc out

[arc]

If I didn't make it clear, I ordered 20 more magnets so I now have 40 neos total (20 per rotor).
Hopefully with twice the number of neos and with the the channeled flux ... along with some coil testing I'll get better results than would be possible with the initial plan.

Wish me luck,

arc out

[just-doug]

before you wind to many coils,it a good idea to do a life size drawing of the statore so you can know the exacte size and shape of coil that will physically fit.look at the postings by chris olson on here.

[arc]

Hi Doug,

Yup, I made a full sized drawing but I will admit that getting all 15 coils to conform to it was a bit of a challenge (at this size [6.25" magnet circle] things don't need to be off much to cause headaches ... considering 20 polls and 15 coils).
Coils are all wound and I made a jig with 15 dowel pins in a circle to form the coil assembly nice and uniform.
Taped all the coils together (that was a pain) and placed some epoxy where they join so I now have a coil set that is manageable and conforms to my magnet circle.

Made a 3 layer stator mold from 1/4" thick hardboard (stator should turn out ~1/4" thick plus a sheet of fiberglass each side) and the coil assembly fits in the mold nicely.
When the epoxy sets up a bit more, I'll solder my coils per phase and make some connection sleeves from some small copper tubing, lay in a sheet of fiberglass, place the coils, make the pour, lay in another sheet of fiberglass and clamp 'er down good. (I'll tape the edges and wax the mold for easy release).

As you can imagine, this mini axial flux is turning out to be nearly as much work as a full sized unit (and, of course, will not produce as much power).
I'm enjoying the process, however, and am on a very low budget so I'll be happy with the results even if the output is not generous.
(My goal is to light some LED's for the deck, if I can charge my mouse batteries as well ... I'll be a very happy camper  ).

Wish me luck on the pour.

Arc out


.

[arc]

Hi All,

Progress Report:

Stator has been cast, I'll leave it for 24 hours before checking but it should turn out nice and thin (1/4: mold).I placed screws around the perimeter of the mold and around the center disc of the mold, spacer to clamp things down nice and tight.
I checked continuity and for shorts before casting and the 1/4" copper sleeves should work well as contacts at the ends of each phase.

I really  hate working with the fibergalss resin but as soon as I get the rotors cast (to keep the magnets ins place I'll be done with that stage.
I'll add some 1/8" brackets to mount the stator and should be ready to do some better testing to determine voltages, amps etc.
The coil resistance per phase is 1.2 ohms. so I hope that will not be a problem (hopefully what is  to be expected using #20 AWG.70 turns and  5 coils per phase.). Nothing to do but wait to see how the stator turned out.

Timber