Posted by Michael B on December 20, 2009, 2:56 pm
Sorry about the kinda-duplicate posts. The first one appeared
to have been lost.
Posted by Josepi on December 18, 2009, 3:27 am
Sailboats often go faster than the wind when they cut across it.
> Michael,
"No problems with overspeed, it won't be going faster than
> the wind
Posted by BobG on December 17, 2009, 8:20 pm
> However, there is a problem here with wind turbines, they have to work
> at various wind speeds.Ideally they would be allowed to speed up as
> the wind speed increases but this is not possible for electrical
> reasons (if generating AC).
==========================
===================
But if the turbine has field control, the drag on the blades can be
modulated to take advantage of hi and low wind speeds. The wild ac
output can be rectified and inverted very efficiently.
Posted by Josepi on December 17, 2009, 10:43 pm
If the wind turbine outputs AC for grid-tie it would usually have a deisel
or other fuel engine in the turcell (sp?) to keep the AC syncronized to the
grid.
Most smaller wind turbines put out AC three phase and have circuitry to
adapt to varying wind speeds. They put out nothing, most of the time and
huge amounts of energy in windy times.
I built a voltage double for my unit and it puts out some power in light
winds. In heavy winds the full wave rectification puts out normal voltages
and supercedes the voltage doubler circuitry. This circuitry has been
patented but any half-decent electronics person can create a multi-phase
full wave voltage doubler for you.
But if the turbine has field control, the drag on the blades can be
modulated to take advantage of hi and low wind speeds. The wild ac
output can be rectified and inverted very efficiently.
> However, there is a problem here with wind turbines, they have to work
> at various wind speeds.Ideally they would be allowed to speed up as
> the wind speed increases but this is not possible for electrical
> reasons (if generating AC).
Posted by harry on December 19, 2009, 6:10 pm
> If the wind turbine outputs AC for grid-tie it would usually have a deisel
> or other fuel engine in the turcell (sp?) to keep the AC syncronized to the
> grid.
> Most smaller wind turbines put out AC three phase and have circuitry to
> adapt to varying wind speeds. They put out nothing, most of the time and
> huge amounts of energy in windy times.
> I built a voltage double for my unit and it puts out some power in light
> winds. In heavy winds the full wave rectification puts out normal voltages
> and supercedes the voltage doubler circuitry. This circuitry has been
> patented but any half-decent electronics person can create a multi-phase
> full wave voltage doubler for you.
> But if the turbine has field control, the drag on the blades can be
> modulated to take advantage of hi and low wind speeds. The wild ac
> output can be rectified and inverted very efficiently.
> > However, there is a problem here with wind turbines, they have to work
> > at various wind speeds.Ideally they would be allowed to speed up as
> > the wind speed increases but this is not possible for electrical
> > reasons (if generating AC).
A "propellor type" turbine blade tips can exceed wind velocity.
Another problem is that the power available varies as the cube of wind
velocity.
ie, if the wind speed doubles, there is not twice the power available,
but eight times the power. The turbine will then revolve not twice as
fast, but four times as fast. (Assuming constant torque.)
This is the reason for extreme precautions for over speeding, eg outer
sections of the blades being independently reversible too control
speed.
Also google "assynchronous generator" ie induction motors used as
generators.
XML site map
>