alternative alt

[stop4stuff]

Hi All,

Continuing my ideas for an alternative style of alternator.

(see: http://www.fieldlines.com/story/2004/6/10/104827/029 )

Unless anyone can say "it's been done before, it's called a..." then I'd like to name this type of alt as a 'Raxial alternator', being cpable of generating electricity in a coil either radially or axially (or both).

The diagram below represents 12 1"x1/4"x1/4" neo block magnets radially opposed, set in a non ferrous rotor.

And here's the rotor. 12 neos superglued into 2mm x 3 ply acrylic (6mm thick).

The images below show the flux lines for the rotor.

For the initial testing I used a coil of 100 turns, 24SWG wire (approx 6x6mm leg) and spun the rotor up by hand.

200rpm yeilds 0.3v AC open and 0.2A AC shorted

Now the dilema I face...

Which coil setup should I go for?

8 coils per side, 4 phases of 4 coils each.

6 coils wrapped over, single phase.

8 coils wrapped over, 2 phases of 4 coils each.

Any suggestions?

or should I try 'em all?

And does anyone have any pointers about eddy currents, what they are, what causes them, how they affect output, etc.?

thanks

paul

[tecker]

   I've been using Hard rive magnets for some time now it looks  the wave shape

 sud jests  both poles together cancel and drives a high inductions pos ( or neg depending on the coil orientation) and very little neg so so end up only being able to use half of the induction cycle with large coils I know  this somewhat vague but I 'll be interested to see what you get I may be doing something wrong. The coils I am winding now are small rectangles so there is a complete collapse of the field with as the magnets pass.

[stop4stuff]

Today I made a rough'n'ready wrapover coil, 25 'turns' 20SWG wire. The coil was held together by wire bag ties (ferrous wire).

A couple of results...

Single coil, 25 turns 20SWG wire, short circuit across the meter (short voltages

900. rpm, 0.230v AC @ 4A AC = 0.92W
     
1100. rpm, 0.308v AC @ 5.25A AC = 1.617W )
      
      

I'm not sure what effect the wire ties had.

Judging by the results so far, I'm going to order in some 21,22 & 23SWG wire. I'll be aiming for 70-100 turns (probably 22) & try out the 6 & 8 coil configurations.

paul

[PHinker]

Paul,

   You're thinking along the same lines as I have been kicking around for a couple years.  My design has the magnets embedded in the rotor with the north and south faces pointing out parallel to the shaft.  The coils are wound over laminated silicon steel 'C' shaped sections that straddle the rotor.

One problem with this design is that fabrication is difficult.  Advantages would be that the coils can be exposed to alot of airflow so cooling would be good.  You could minimize cogging and iron losses by using grain oriented silicon steel laminates and spacing the laminiates so that there are at least two per magnet.

I've really enjoyed reading your posts concerning the prototyping you're doing with the legos.  Very interesting!

Paul

[commanda]

The normal way to express voltage & current from a coil is;

open circuit voltage.

short circuit current.

What you are showing with your 2 meters is the voltage generated across the shunt in the meter which is measuring the current. Multiplying these 2 numbers together to get watts is not valid. The voltage will vary depending on which meter you use, although the current won't vary by much. If one were to use a theoretically ideal current meter, with zero internal resistance, the voltage would be zero. By playing ohms law with either set of figures you have given, shows your current meter has an internal shunt resistance of approximately 0.058 ohms. Part of this is also probably lead resistance, as I assume you have the voltmeter connected to the clip ends of the leads from the current meter.

The open circuit volts will normally be a linear function of rpm (volts per rpm). Once you have a figure for open circuit volts at some rpm, and the number of coils in series in each phase, and the battery voltage, you can calculate the cut-in rpm.

Amanda

[ghurd]

Hi Paul,

Still thinking about this one?

Did you see my "Another Silly Idea" a week or so ago?

Anyway, along the same lines.

""One problem with this design is that fabrication is difficult.""

Not so I say!  The bugger in you drawing looks a lot like a cheap shaded pole motor, like a fan from a microwave.

Long ago, I put 2 magnets on a rotor, N-S, and rotated it between the lams.  More like a conversion rotor than an air gap rotor.  It 'almost' worked, and I think more time and better tools than I have could make it work.  I thought it would work a lot better with all those turns, but had very low voltage.

Not sure how the size of the rotor (ie lam direction to magnet motion angle) would affect things with the eddy currents.

If you have done anything with a setup like this, please post it.

G-