620 VDC [RE-wrenches]

[Walt Ratterman]

Drake:

I believe that if you are within the United States, this is not feasible
(exceeding the 600V limit).  This is quite hard and fast NEC rule that has
been in place for many years.

I suppose you could pursue some issues with using high voltage wiring (rated
above 600V), but I believe you would be a pioneer in this, and you may not
find it worth the extra 20 volts.

If you are going to go this route....push for 1000 volts.  (like some other
countries are doing.)

Just my humble opinion....

Thanks,

Walt Ratterman
SunEnergy Power International
www.sunepi.org


-----Original Message-----
From: Drake Chamberlin [mailto:Drake.Chamberlin at redwoodalliance.org] 
Sent: Thursday, June 26, 2008 12:38 PM
To: RE-wrenches at topica.com
Subject: 620 VDC [RE-wrenches]


Hello Wrenches,

Some inverters are able to withstand voltages above 600 VDC.  The 
Solectria 95KW can take up to 620 VDC without harming the electronics.

If we size a system so that the record low temperature is gives a 
voltage of under 620 VDC, a viable system can be installed.  There is 
a question, however, about the Code compliance of this, since 
building wire is rated at 600 volts.  Higher voltage wiring is 
available, but will likely not be cheap or convenient to use.  Also, 
what about 600 V modules and PV cable?

Since this is DC, there are not any cycles to create a voltage 
peak.  A 600 VAC RMS nominal system can have (if my calculations are 
correct) a peak voltage of close to 850 volts.  Also, system voltages 
can range up to 10% from the nominal, resulting in voltages of as 
high as 660 VAC RMS on 600 volt systems.

The question is, "can we have a system with a possible 
low-temperature, open circuit voltage of 620 VDC with wiring and 
modules rated for 600 volts?  Can the other 20 volts be considered 
within the nominal range?

Thanks,

Drake 


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