Well said !
except that rings in an alternator are called 'slip rings', not
commutators. The 'commute' part of a commutator is that it switches the
circuit from one coil to another as the armature rotates, but slip rings
don't.
In a DC generator, the commutator effectively acts as a mechanical
rectifier, which is required because the current/voltage in the windings is
actually AC.
An alternator works on the same principles, but since it uses an electronic
rectifier, the current generating windings don't have to rotate, and the
slip rings only carry the excitation current. Thus, it has a magnetic
field rotating inside a coil, instead of a coil rotating inside a magnetic
field.
Bad diodes are certainly a likely explanation for a warning lamp at idle,
but brushes are easier to check <g>
On Thursday, June 10, 1999 8:37 AM, Malcolm Walker
[SMTP:walker05@camosun.bc.ca] wrote:
>
> Yes, there's brushes in an alternator! However not quite in the same
> arrangement as a generator- in a generator (and an electric motor) the
> brushes ride on a shared commutator; this is so that the polarity will
> switch on the armature and cause the motor to turn, OR so that the
> polarity will switch and cause the generator to ...uh... generate.
>
> In an alternator the brushes ride on seperate commutators. The principle
> is the same- a magnetized armature being flung around in the magnetic
> field of a magnetized stator winding, causing the movement of electrons
> (Electricity!!). This electricity has to be let out of the alternator
> somehow- so there's 2 brushes in your alternator. In GM alternators the
> brushes ride side-by-each down at the endbell of the unit, in Mopar
> alternators one rides on the shaft of the armature and one rides on a
> circular platter on the rear face of it... and I've never had the joy of
> dismantling (or mantling) a Lucas alternator.
>
> -Malcolm
> * There is a FAQ for this list! Its new home is:
> http://www.islandnet.com/~walker05/triumph/trfaq.htm
>
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