Low Output Axial Flux

[Kevortex]

Hey Guys,

I appear to be have a low output problem compared to what I have read in the OtherPower articles of similar generators.

I've built an axial flux gen using a 15" rotor with 12 poles - 1"x2"x1/2 thick" N45 grade NdFeB magnets. They are properly oriented N S N S N S ....the rotor is made of wood. No iron in it.

The coils are made from 120 turns of # 14 ga. wire, 9 of them, 3 phase, Delta wired (I've tried Star wiring too). No iron in the coils cores. The inner diameter of the coils is the same size as the magnets (1"x2"). The coils are not fiberglassed into a mould, they're just mounted in place.

When I use a plain ole analog VOM meter set on the 10 volt AC range, I am hard pressed to get 1 volt when I spin it good by hand. This is the same no matter which output taps I use.

I've tried checking my wiring to make sure I'm not cross wired or something.

If I short the output connections together the rotor is VERY hard to turn so I must at least have something wired correctly. I hooked up a small LED to two of the outputs and it barely lit up.

I even tried spinning all 12 poles past only one coil. I could get 1 volt if I tried hard enough.

I'm stumped.

What am I doing wrong. What do I try next?

Thank you,

Kevortex

[Shadow]

Not an expert here, but I think you need some metal in the mix. Try mounting your magnets on metal rotors as opposed to wood.

[Jessum Dumguy]

 Ya an Iron backing for your magnets will help alot,

3/16 to 1/4 inch thick I'd figure. If I read your post right it's

a single rotor, Laminants behind the coils might add some aswell.

Also, You say;

 "The inner diameter of the coils is the same size as the magnets (1"x2").

Thats groovy but insure that the coils legs are spaced over the

centerline of N-S pair of mags. ( More important than center hole).

Each leg starting over the two mags and leaving the two

mags at (roughly) the same time.

.

[windcruiser]

I hear the word HARD in your explanation. Check your phasing and make sure all the coils are equally oriented (clockwise or anti-clockwise wind)if you have one coil upside down it will reverse the current and you will definetley have less power and the machine will be hard to turn. Check your phases what hapens when you do a delta or start connection -- is the machine hard? Some iron is always good behind the coils or a second magnet rotor. as others have stated use metal disks for rotors.

simon

[Flux]

The others are right about the lack of iron, you are not going to get much power in its present form but I think you have a connection problem as well.

I don't exactly follow the wording in places but you give the impression that you get the same volts from one coil as from the complete winding. This and the fact that it is very stiff when shorted makes me think that you have wired the coils in parallel not series.

If you have 1v from 1 coil when you connect the 3 coils of 1 phase in series you should get 3 volts. If you star connect you should get about 5v.

For each phase you should join the 3 coils start to finish, start to finish. I think you have joined all the starts together and all the finishes together as a parallel winding.

When you have got the connections right you will get a big improvement by mounting your magnets on a steel disc. To get best output you will need another disc spinning at the back of the stator or a fixed laminated disc.

Flux

[Jon Miller]

Well I have just put my 7' 'old style' designed turbine up with out the coils to test the laminates that I spent a week or so making.  well these laminates below are made from a microwave transformer.  One transformer did the holw of mine but you will need more as your rotors are bigger.  I think the pic explaine them selfs.

This is the frame to poke the laminates in lots of fun

and this is them completed.  they have been cased into resin to protech them but the turbine dosnt have any problems turning with them next the 12 1" mags i have.  the gap is 5mm or so.

Oh this is a pic of it in its temporary home for now so i can test and make coils etc...

well hope this helps:D

Jonathan Miller

[Vernon]

The fact that it is hard to turn when shorted argues for sufficient flux and would indicate that you don't need iron to generate more than a volt. I would test the output of each individual coil then connect one leg ... check its output ect..

 

[Kevortex]

Hey Jessum,

You brought up a good point about the leg/alignment. Just so we are on the same page, will you please define what you mean by "legs" of the coils?

Yes, it is a single rotor.

Before I go off and do something stupid, I'd like to clarify things. :-)

My original thoughts were to leave the coils air core to reduce the cogging effect. But, if I need laminates, so be it. I'll add laminates.

As for the iron backing for the magnets.... can I add an iron ring (that spans the diameter of the magnets)or must it be a disc the full diameter of the rotor?

I plan to make one change at a time (starting with the coil/magnet spacing) to see what works.

Thank you in advance,

K

[Kevortex]

Well,

Fortunately(unfortunately?) the coils are all wired in the same direction and wired together correctly. The rotor becomes difficult to turn in either delta or star wiring configuration, Which is what any permanent magnet motor will do if the leads are shorted. I think Jessum is on to some thing. Read his post and my reply.

I'll keep checking back here untill I get it right.

Every ones input and help is greatly appreciated.

Every one that replies to my problem, please add my post to your HOTLIST and I'll keep checking back.

Thank you!

[Kevortex]

Yes, I agree with you. My understanding is that : the higher the flux density I have , the greater the opposition to turning the rotor will be when the leads are shorted.

I will do as you suggested-check the output of one coil at a time and add from there.

Read Jessums' post as I think he is on to something. I think my coil to magnet spacing is wrong, if I understand him correctly.

The good news is, to correct the spacing problem, I could add a magnet between each one of my exsisting magnets (yes, I have that much space between the exsisting magnets). THEN the coil/mag spacing would be correct if I have calculated correctly. I would of course re-orient the magnets to N S N S N,,,,

Then I'd have a 24 pole , 9 coil, 3 phase generator.

(My mind experiences elation as I contemplate ungodly amounts of high current output from this). teeheehee

Thank you

BTW...

Please add this post to your HOTLIST.. I'll keep checking back to this board till I get it right.

[electrondady1]

google search the board under "electric ed" he posts some very clear multi color coil/mag lay out diagrams . also try coil design or mag spacing   its not easy to understand every thing at first . you can google search the board like it's a university library. here's a tip that helped me , make a scale drawing of your mag layout. make another of your proposed coil lay out on traceing paper thumbtack them together at the center point and move them around .

[Kevortex]

Exellent Advice.

At this pont I think my mags are spaced too far apart for my coils to align properly with.

Research shall tell.