Yet another braindump

[Spdlmt150]

I was looking at the 1.25 X .562 magnets and started thinking about the narrower coil thing. If many smaller mags are used to increase the amount of copper in field, decrease the amount of copper out of field, would it work?

28 magnets, 21 coils, 7 coils per phase. At the expense of making assembly a real pain, would this be a more efficient layout than the 12/9? Less heat generated?

$90 of magnets for a dual rotor.

I will definitely consider ordering more of these size mags if this could put out some useable amperage. Any guesses as to the potential for this?

[RP]

I think you might be up against an air-gap limit now.  

Consider that the magnets are now quite close to each other.  Unless the air gap is smaller than the gap between adjacent magnets I'm concerned the flux may simply go sideways rather than through the coils.

For a high voltage machine it may work if the coils can be thin enough (few enough turns) to use a narrow gap between magnets.  With so many poles it should be somewhat easier to get the volts up anyway.

My two cents...

[Spdlmt150]

I'm shooting for 12v. High voltage has it's advantages. I'm still looking at simple 12v batt, inverter.....

[Flux]

Efficiency and heating is an issue of how much you try to extract from a given size machine and little to do with the size and number of magnets.

For a given set of discs and a given speed you can alter the number of magnets over a fair range for similar results as long as the volume of magnet is similar.

I agree with RP that you will be worse off with too many small magnets. You will have more leakage flux and you will also loose out with small magnets because the flux in the surface region is lower than in the bulk of the magnet and with small magnets a lot of the material is in this surface region.

The only case where you may benefit is if you are forced to use transformers, where the higher frequency will make life easier.

The 2 x 1 x 1/2" magnets tend to be far more cost effective compared with odd shaped things and you will do better to stick with them. Your tiny magnets will probably be thin as well as small. Thin magnets are not cost effective with air gap designs.

Flux