SMA and transformer [RE-wrenches]

John Berdner jberdner at sma-america.com
Mon Sep 8 09:26:14 PDT 2003


Daryl:
 
The utility is supposed to keep the voltage within 95 to 105% of
nominal at the Point of Common Coupling (PCC).
The location of the PCC may be critical here since they will not be
responsible for voltage drop in the customer's wiring.
They are allowed "infrequent excursions" outside this range (ANSI Range
A).
Every time the air conditioner comes on is not infrequent.
If they will not fix it then ask them for a letter that allows the
inverter to operate outside of the IEEE 929 limits.
If you can get a letter then we can adjust the inverter's set points.
 
Adding a transformer will add losses to the system and should be
avoided if possible.
It sounds like the sag is occurring only on one side of the split
phase.
Using the transformer to connect the 1800 to 240 Vac will help to some
degree if the other half of the split phase is staying up.
I am not sure if it will solve the problem though because it sounds
like the utility impedance is pretty high.
 
Best Regards,
 
John Berdner


>>> daryl_solar at yahoo.com 9/5/2003 05:45:43 PM >>>
Thanks to all for response
Several asked why do I care, and here is more of the
story; the customer lives on a back road. his power
will drop to 109 volts with the room air conditioner
on. Or toaster or whatever. I made the mistake of
selling him a SB1800 when I should have sold a SB2500
but I did not come up with this 120 volt vs 240 volt
problem. He has a 1200 watt solar system, that is all
that he had money for and his good exposure was for
only 1200 watts. He is willing to work to maximize
the solar for his live style. Using electricity
during peak sun. 

My choice is to put as much of the heavy loads on one
leg? My voltage would really sag on coincidence. He
is served by a REA-Coop, who say the power is fine?

But in the end the customer is King. And I want to
serve this percieved need. So does anyone know, will
a T-240 or a X240 help or even work?

Thanks again.
And I am pursuing the utility problem, and will send
what I come up with. 
Daryl 



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