Isn't the terminology technically that "dynamos" generate DC and
"alternators" generate AC? Having understood that, do the "alternators"
in our cars generate AC or DC? What you're describing, Dan, sounds to me
like the operation of a DC generator. In a DC generator, as in a DC
motor, there are two bent pieces of copper separated by a narrow portion
of the plastic of the rotor. The brushes are directly opposed to each
other, so that each is always contacting the opposite plate or neither.
Since each brush is always connected to the end of the armature passing
through the same field (for that brush), the current flowing through that
brush always flows in the same direction.
In an AC generator, as in an AC motor, there are two complete rings. Each
brush is connected to a different ring. Since the rings, and therefore the
brushes, never trade the ends of the armature to which they're connected
while the ends of the armature move from one magnet to the next, the
current reverses direction.
So, what you're describing, Dan, doesn't sound like conversion to DC, but
the actual generation of DC. Can anyone explain whether car "alternators"
generate DC or rectified AC?
Jim Ruwaldt
'72 TR6 CC79338U
Bloomington, IN
On Fri, 31 Oct 1997 DANMAS@aol.com wrote:
> In a message dated 97-10-31 07:22:35 EST, jruwaldt@indiana.edu writes:
>
> > I understand all that, but why do we call them "alternators", when they
> > produce direct current?
>
> Jim:
>
> As a matter of fact, generators also produce AC voltage. The conversion to DC
> is provided by segmented slip rings, rather than diodes. Just as the
> generator rotates to complete the positive cycle and begin the negative, the
> brushes slip from one segment to the other, reversing the polarity of the
> output. The generator ouput is reversed by rotation, and reversed again by
> the brushes, so the end result is a constant polarity output, or a pulsating
> DC, just as in the alternator.
>
> NOTE: The following contains NO LBC content!
>
> For all you Steve Vai and Joe Satriani wanna-bes, this is how the humbucking
> pickups on your guitars work. Each pickup consists of two seperate pickups,
> wired together. The magnets in each are placed in opposite directions, the
> south pole of one next to the north pole of the other. When a string is
> plucked, the output produced by the magnets is of opposite polarity. However,
> the wire coils are also wound in opposite polarity, so the signal is put back
> in phase, and you get the full output. When electrical interference is
> encountered, such as you get when playing in a room that is lit by
> flourescent lights, the output signal generated the electrical fields cutting
> through each winding is cancelled because of the polarity reversal of the
> winding connections. The magnets are not involved in picking up interference.
> Les Paul was a clever guy!
>
> Dan (a frustrated Vai/Satriani wanna-be!) Masters
> Alcoa, TN
>
> '71 TR6---------3000mile/year driver, fully restored
> '71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
> http://www.sky.net/~boballen/mg/Masters/
> '74 MGBGT---3000mile/year driver, original condition
> '68 MGBGT---organ donor for the '74
>
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