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       #Post#: 2801--------------------------------------------------
       Where is the loss of efficiency in a Turbine?
       By: lynx wind Date: May 17, 2014, 1:01 pm
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       This may be interesting for some.
       If you calculate the output of just the Gull 160 alternator
       based on its OCV and rpm it is about 31% efficient at 30-32 mph.
       It takes 614 watts to turn the alt and produce 185 watts.  If
       you back calculate the power in the wind for the Gull 160 at
       30-32 mph - 614 watts is 41% efficient at the turbine.  There is
       about 1500 watts of power in the wind (2 HP)
       Theoretically a wind turbine can't be more than 54% efficient
       (the Betz limit).
       What this means is the biggest inefficiency for the Gull 160 is
       not the blade and rotor design, it is just the physics of
       converting the kinetic energy to electrical energy.
       The Gull 160 wasn't designed to be its most efficient in 30+ mph
       winds.  It was designed to operate well in 12-20 mph winds.  As
       a comparison the UGE wind turbine is about 15-20% efficient at
       best and they make no apologies, but rather they favor
       aesthetics.
       This brings up the idea of designing the alternator to be more
       efficient at higher wind speeds and rely on a boost system to
       capture power at lower wind speeds.  This is another reason to
       stick with the single phase alternator.  The boost rectifier
       described by Nessprojects is so simple and it works very well.
       #Post#: 2819--------------------------------------------------
       Re: Where is the loss of efficiency in a Turbine?
       By: burnit0017 Date: May 18, 2014, 9:09 am
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       Hi, any thoughts on the braking effect that is created by the
       reverse EMF at the PMA?
       #Post#: 2820--------------------------------------------------
       Re: Where is the loss of efficiency in a Turbine?
       By: lynx wind Date: May 18, 2014, 10:00 am
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       Yes, as the magnets pass the coils a current is induced in the
       copper coils which flows through a load (battery GTI or
       resistive load) and in turn creates an opposing force to the
       magnets travel.  (Lenz Law) This is what takes kinetic energy
       (power) to overcome.
       The other braking effect would be if the alternator output is
       shorted and the turbine turns at all.  There will be zero
       voltage and just current flow.  This creates a very high
       opposing force to the magnet rotor and will consume all the
       energy put in.  This is how wind turbines are stopped in high
       winds or for servicing.
       Some wind turbines use a thermal sensor to trigger the braking
       when the stator gets too hot.
       I have seen 40-60 rpm with the Gull 160 in high winds even with
       a dead short.  This takes several HP and you couldn't do this by
       hand.
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