Reversed phase two- less voltage

[Gunson]

Hello enthusiasts!

I made an 3 phase alternator with 3 coils in every phase. Number of magnets are 12. It's in star-winding. Everything seemed great when testing and from what I learned afterwards, I succeeded to get some things right; coil's hole about the same as the magnet and not two magnet poles over one coil-leg.

Although I get a lower voltage reading when the second phase is connected same way as phase 1 and 3.

Connect:

start A, B, C-out, end 1, 2, 3-together. This gives 12 V rectified Volts, 200 RPM

      A, 2, C-out      1, B, 3          gives about 10 V,                 200 RPM.

I don't have a good reading of the current if this might be the answer(?), since the resistance in my multimeter is a bit too much for a long duration with my drill-tester.

Why is this? What are the consequences?

I havn't got a hold of a descent battery so I can't tell if I'm happy with the results yet.

Greatful for any help from this great site

Gunson, Sweden

[Gunson]

BTW  here is an image of the coil positions.  

http://www.otherpower.com/images/scimages/13223/spolar.jpg

[CmeBREW]

Hello,

      I'm still having a hard time understanding how you hooked it up.  Did you hook A,B,and C together  like the following diagram.(Which is 'STAR' hook up)

  And then X,Y, Z are the 3-phase 'out' wires?? (Or the reverse is the same 'Star' effect-- by hooking X,Y,Z together and using A,B,C as the 3-phase 'out' wires)

 

Can you explain again what you did using this diagram?

It almost sounds like you may have a coil reversed.  

[Flux]

"Although I get a lower voltage reading when the second phase is connected same way as phase 1 and 3."

I think you are mixed up. With these windings all phases are connected the same.

"start A, B, C-out, end 1, 2, 3-together. This gives 12 V rectified Volts, 200 RPM"

This is correct

 " A, 2, C-out      1, B, 3          gives about 10 V,                 200 RPM."

This is a 6 phase connection. It doesn't work with this winding. It does work with fully wound motor stators where the physical displacement is 60 electrical degrees. It is a common trick in this case to reverse the centre phase rather than take the end connections from the electrical 120 deg points which are not adjacent pole groups.

The ac voltage between any pair of output leads should all be the same if it is balanced 3 phase. In your second connection you will have strange voltages if you measure line to line but the volts from lines to neutral will be equal in both cases.

Flux

[Gunson]

thanks for the replies!

To begin with, my understanding was that a three phase stator SHOULD be wound with reversed in,-output on the second phase. If that in fact is a 6-phase machine, and the image CmeBREW shows is for 3-phase. Then there's no problem and everything's working like it should!

"Although I get a lower voltage reading when the second phase is connected same way as phase 1 and 3."

Yes FLUX that is mixed up...what I meant was higher voltage, when connected the same.

So, just to be sure. There are no reversed coils in a 3-phase stator?

Thanks for clearing this up

[Gunson]

Now I found the link where I got the idea from:

http://www.windstuffnow.com/main/3_phase_basics.htm

[Flux]

If you take  a machine with as many coils per phase as poles then it will be basically three single phase windings. To get 120 electrical degree displacement you need to choose 3 coils for the star point that  are not adjacent. The adjacent ones are spaced at 60 electrical degrees. It is usual to take the first and third coils as A and C. If you take the coil between them as B it will be of the wrong polarity and you need to reverse connections to the B phase.

If you only have coils under the magnets of the same polarity ( an alternative winding for 3 phase motors with half the coils then adjacent coils come up as ABC. These single layer axial windings in fact leave out even more coils so there is 1/4 of the number of coils of 3 basic single phase windings.

This single layer arrangement also works out with coils of each phase that come up ABC.

Only in windings that have 3 times as many coils as magnet poles do you get the 60 degree displacement where the easy way is to reverse the middle phase. If instead of taking the 3 adjacent coils for the star point you choose those 120 electrical degrees apart the thing comes out as 3 phase and no coils need reversing but starting with adjacent coils is common practice. If you looked at Ed's 2 layer windings you will find the case where the easy way is to reverse the B phase but it never happens with the single layer air gap machines.

I know this is confusing but it is mainly European 3 phase motors that have ther full coil arrangement. Most N American machines seem to be wound with coincident poles with half the coils. There are of course always exceptions to cause confusion. I hope this helps.

Flux

[Gunson]

wow  

thanks to FLUX

You seem to have an insight vision of the electric matter.

Yes, that was confusing and I will sure look it up.

   It is the very process of the magnetic power making induction in the copper that I'm most curious about in the wind power business.

and there's a lot to learn there...