three way power [RE-wrenches]

[Hugh Piggott]

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Kurt,
>
>I'd love to hear comments regarding the feasibility of sending power
>from a shared wind generator to three homes, each about 300 feet from
>the tower site.  Specifically I am wondering if each home could get one
>leg of the three phase wild ac off a high voltage machine.  Each home
>would transform the one leg down to system voltage (24) and rectify to
>DC.  The battery, which currently has PVs at each location, would be
>regulated with an Enermaxer.  Would this work electronically and might
>the machine have serious problems with any uneven loading(?) of the
>windings?

This would work.  There would be some phase imbalance due to the 
different battery voltages, and this could cause unequal currents and 
thus the alternator to grumble if it got bad enough, but I doubt if 
it would be noticeable.  The cost of the transformers would be lower 
this way, than if you used 3 transformers (or a 3-ph transformer) at 
each site.

Connect the transformer primaries delta for best transmission 
voltage.  Or connect them star (wye) to minimise harmonic currents. 
I am not sure which wins out.  Either way the transformer turns ratio 
has to be chosen correctly for battery voltage which may require some 
scratching of heads.  It has to be able to cope with low frequency 
operation, but this is OK so long as the voltage is proportionately 
low too (compared to 60Hz, 120V or whatever the transformer is rated 
at).

In any situation where you use a transformer on a permanent magnet 
alternator, there will be some impairment of startup due to the 
reactive current sloshing around in the transformer at all speeds.  I 
usually try to include a cutout which disconnects the transformer at 
low revs.  But this may not be necessary if low cut-in is not 
critical.

The battery will not work so well under these distributed conditions 
as it would in a central location.  Some systems will be dumping when 
others have need for charge.  Some will go flat when others have 
energy left.  Using 3 separate batteries  helps with sharing energy 
fairly (if that's an issue), but it would be more efficient to have 
one big battery (and one big inverter). A centralised system would 
need bigger cables than the system you propose but could offer 
benefits where there is a lot of diversity in loads.
-- 
Hugh

hugh at scoraigwind.co.uk
http://www.scoraigwind.co.uk/

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