contactor cuestions [RE-wrenches]

[Jerry Caldwell]

Marco,

Xantrex says they will be including an automatically
disconnecting contactor with all PV series inverters
soon.  SMA's Sunny Central will also have this feature
when it is released.

The Sunny Central looks like it will be the superior
product, but will only be available in one size at
first.  The Xantrex guys are looking to improve their
product as well.  I'm sure we'll hear from both
manufacturer's soon, as this issue was addressed by
both at Energy Outfitter's training conference in
Vegas.

Jerry Caldwell
Light Energy Systems
Concord, CA


--- Marco <marco at pvthawaii.com> wrote:
> 
> 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

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