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Hey do you know your car's alternator only outputs 7-10% while it's running? - Page 10

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Posted by Fred Abse on August 9, 2009, 3:12 pm
 
On Sun, 09 Aug 2009 00:24:02 -0700, Archimedes' Lever wrote:


No. Permanent magnet rotor, windings on the stator. Still an alternator.

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
                                             (Stephen Leacock)

Posted by John Larkin on August 9, 2009, 5:51 pm
 
On Sat, 08 Aug 2009 19:37:38 -0700, Archimedes' Lever


Google "ungeared wind turbine" and confirm that you are always, always
AlwaysWrong.

Hey, catching your mistakes is both fun and educational.

John



Posted by clare on August 10, 2009, 2:43 am
 On Sat, 08 Aug 2009 19:37:38 -0700, Archimedes' Lever


 A Piggott wind turbine is direct drive - and since a Piggott wind
turbine most definitely exists, by deduction it is clear that NOT ALL
wind turbines gear up the rotation ratio. There are many other "plans
built" wind turbines out there that are also direct drive (and I am
certain also at least several commercial units in the low - mid power
range)

And if the governor limits blade speed, what does that do to
alternator speed???
Are you aware of any wind turbine employing a CVT??? (contantly
variable transmission)

Posted by harry on August 10, 2009, 6:16 pm
 On Aug 10, 3:43 am, cl...@snyder.on.ca wrote:

Most of the easily available alternators are intended to run at high
speed because they are run off IC engines. So if you're gonna use them
for a wind turbine you'll need a gearbox or belts as the turbine only
turns slowly.  However belts & gearboxes consume power so if you can
do without, it's obviously much better.
A slow speed alternator is perfectly easy to design, it just needs
more poles & probably would have to be a permanent magnet job. However
as it has lots of poles (and lots of turns of wire on these poles) and
will  be bulky and expensive especially as they will never be in mass
production.
Lots of very large wind turbines control their speed by rotating the
outer half of the blade. They can even be stopped by this method.
The problem revolves around the fact that if the wind goes twice as
fast the power available is not doubled, it is cubed, ie x8.   This
leads to major control problems

Posted by Fred Abse on August 9, 2009, 3:12 pm
 On Sat, 08 Aug 2009 21:59:15 -0400, clare wrote:


Still *some* power, though.

Take a look at: http://lees.mit.edu/lees/posters/RU2d_Caliskan.pdf  for an idea
of what automotive alternator characteristics look like.

That document also describes the use of switched mode rectification to optimize
output power, and postulates an expression for output power which is a reasonable
fit to experimental data.

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
                                             (Stephen Leacock)

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