Re: Questions about size of magnetic wire to use

On 21 Oct 2005 06:06:30 -0700, ewitte@xxxxxxxxxxx wrote:

>What about this? Make 54 individual coils. Pair up each three so
>there is no gap in electricity. After all thats the purpose of 3
>phase. So there is always something going on. Then continue over 18
>more times. I can use individual diodes with less voltage drop for
>each output instead of bridge rectifiers. That way wouldn't it be
>closer to 1.46 amps per coil?
>
>Eric

One big advantage to three phase is "no gap in electricity" as you put
it - that translates in an easier to move load, less tendency to
"cog," as each magnet moves past a pole piece.

You may want to rethink the diodes. Silicon diodes drop less forward
voltage as the temperature rises (if my memory is correct). And you
can buy a three phase bridge rectifier if you wanted to.

You should have no trouble getting 1.5 amps per coil. Unlike a
transformer, an alternator has some airflow around the coils.

So you plan to have one pair of coils (three amps per phase) span
three poles of the stator? With an overlap in coils? (each three
offset by one pole, total of 18 poles?)

I notice in a lot of modern motorcycle alternators they rotate the
magnets around the outside of the stator. That probably helps keep
the wire shorter (use less wire, less wire loss, less heat), shorter
magnetic path length (less iron loss, less heat), and since the
rotating part has a relatively large circumference, the speed of the
magnets passing the pole pieces is higher for the same rotational
speed. Looks easier to build the stator that way.

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