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Generator?
Alternator? What?.
Essentially both are correct. A generator simply
generates electricity. An alternator is just a
specialized form of a generator. The type I'll
be describing for construction is a 3 Phase
alternator. Easy now... It's not that hard. 3
Phase isn't some scary thing that only the geeks
understand. All it means is that there are three
separate generating circuits all running at the
same time, but making electricity at three different
times. If we were to look at the amount of
energy produced by one of the circuits
over time, we could graph the level and it would
look like this .
As the magnet approaches the coil the energy
increases until the magnet is directly overhead
and the magnetic flux, or lines of force are at
their maximum here . Then the
magnets begin to leave the area of the coil and
as such the magnetic energy drops as shown here .
As you can see, with a single "phase"
there are times when there isn't any electrical
energy being generated. There's
"holes" in our electricity. If we were
to add two more "phases", equally
spaced in time we would have a graph like this.
It's pretty easy to see that there is no holes
in this scheme. It's a much more efficient
method of generating electricity. Now there are
a few things that I haven't shown but they are not really relevant
to a basic understanding. What is important to
know is that the energy will pulse as the magnet
travels over the coil and there will be no
energy without the magnet traveling over the
coil. Now comes the cool part... To
get three phase energy we need to have a
dissimilar amount of magnets and coils. We use
the ratio of 3:2. Three coils and two magnets or
a multiple of these. In my alternator I have 12
coils and 8 magnet banks (banks consist of two
smaller magnets). As it spins, the coils produce
energy in sequence. Don't
look at this too long, it's a little hypnotic. As
you can see, only 4 of the coils is really doing
anything at any given time. An alternator
designed like this with no metal as cores in the
coils reduces what is called
"cogging". This is when the magnets
are attracted to the iron inside the coils and
you need to provide a lot of energy to overcome
that attraction. An alternator that cogs will
jump and stick as you turn the driveshaft. One
that doesn't cog will turn very smoothly. This
also translates into less noise. A cogging
alternator will impart a lot of vibration into
the tower and, if it is attached to your house,
into your house as well, causing a really loud
wailing that changes as the wind speed changes.
It's best overall not to have the wind mill
tower attached to the house at all.
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