contactor cuestions [RE-wrenches]

[John Berdner]

Marco:
 
One thing watch out for is the high inrush current to re-magnetize the
transformer.
Make sure the contactor you select can handle this inrush.
It varies by transformer design and is not trivial.
Ask the transformer manufacturer and contactor manufacturer before you
spec. everything.
 
Best REgards,
 
John Berdner

>>> marco at pvthawaii.com 12/5/2003 12:05:24 PM >>>

Commercial grid-connected systems using the Xantrex PV series 3-phase
inverters with their dedicated isolation transformers mean that
there's
going to be a not insignificant parasitic power loss during the
nighttime
hours. According to my own measurements and conversations with others,
this
loss can somewhere between 3-5 percent, or even more, of the previous
day's
kWh production. One way around these inverter and transformer core
losses
would be to install a three-pole contactor/relay that would disconnect
the
PV equipment in the evening and reconnect it early the following
morning.
The issues as I see them are: 1) extra cost for the labor, contactor
and
additional control electronics, and 2) additional means of system
failure in
case the contactor stays open. One could use a photosensor to control
the
contactor or even a standard mechanical or digital timer. 

Has anyone out there gone this route of using a contactor? Any feedback
on
the pros and cons?

thanks,
marco 

Marco Mangelsdorf
President
ProVision Technologies, Inc.
69 Railroad Avenue, Suite A-7
Hilo, Hawaii 96720 USA
(808) 969-3281, fax 934-7462
www.provisiontechnologies.com 






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