contactor cuestions [RE-wrenches]

[Jeff Clearwater, Village Power Design]

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Hi Marco,

You might ask SMA what they use and how they control it.  As I 
understand it from a previous series of posts, their Sunny Central 
achieves no parasitic losses so must disconnect during down time. 
I'd recommend asking Kent Sheldon.  Of course the Sunny Central is 
125 kW but maybe their contactor manufacturer makes a unit 
appropriate for your size.

In the EV industry we use Kilovac vacuum protected contactors for DC 
switching up to 1000 amps.    http://www.kilovac.com/.  I imagine 
they would have long life switching AC.

Hope that helps.

Jeff C.
Village Power Design


>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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-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
http://www.villagepower.com
Sustainable Energy & Water Solutions for Home & Village

Office:  (413) 256-6777,  Cell: (720)480-8455 
Fax:  (413) 825-0372
61 Baker Road
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Boonville, CA  95415
(707) 895-9015
Fax: (707) 897-0224

Council Member - Ecovillage Network of the Americas - http://www.ecovillage.org
Advisory Board - Living Routes - Ecovillage Education - 
http://www.livingroutes.org
Founder:  Ecovillage Research, Development, and Demonstration Program:
http://www.home.earthlink.net/~clrwater/RDD/rdd.html
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