Curious some years ago I was asked to audit a system with a similar design. The question I was asked to answer is why the net kWh exported to the grid was much less than they hoped. The punchine was the idle load on the dry transformers were soaking up about 20% of the PV array's net production.
So from that lesson, I have made it a practice to avoid transformers if at all possible. In fact, a mini-grid retrofit we are doing now involves removal of numerous transformers and to consolidate with 120/208V for all but the deep well pumps and effluent plant we will keep at 600V. What I concluded from this is better to run higher voltage DC lines for the long runs. Haven't had that situation come up again to test. Have others looked into transformer losses? Kevin From: RE-wrenches [mailto:[email protected]] On Behalf Of Darryl Thayer Sent: September-18-18 9:34 AM To: newrewrenches <[email protected]> Subject: Re: [RE-wrenches] Step-up/Step-down Transformer question The single phase - 3phase change is too difficult and expensive. Stay with single phase. I have done this successfully with a step up and down transformer. You, of course, need to select the correct transformer. Transformers seem to have a price advantage using standard voltages. For example, starting at building 240 to 480 and then use 480-volt inverters. This will require longer strings for the 480-volt single phase inverter. another way is to use 240 to 240-480-volt and carry a neutral. then select inverters that can operate with no neutral, I call them floating output. This cuts current in half, voltage drop or rise by 1/4 allowing smaller wire. On Mon, Sep 17, 2018 at 11:42 AM Lorenzo Ortiz <[email protected]<mailto:[email protected]>> wrote: Wrenches, We have a PV array situated about 900' from the POI (240V 1PH). We initially spec'd (5) 11.4kW inverters and the combined output would be 238A. The wire size required for this current over that distance is cost prohibitive. A solution was to use a single 50kW 3 phase inverter at the array and then convert it to 240V... somehow? Is anyone familiar with how to go about doing this? My thought was to have a step down transformer at the POI and pull off two legs to get 240V. Is this even a thing? The other, more expensive option is to use a step up transformer at the array and a step down at the POI to get us a smaller wire size. Thanks for any input. -- Loren Ortiz Commercial PV Designer [email protected]<mailto:[email protected]> (530) 274-3671 [https://docs.google.com/uc?export=download&id=0B6l5VcsZgAv3TXRfSkhpZUNaczQ&revid=0B6l5VcsZgAv3djFpMk9EQUdEdmg1K0hFdHBNZVlTZ3RZdW5VPQ] [http://californiasolarco.com/wp-content/uploads/2018/06/CalSolarADVOCATE.png]<http://californiasolarco.com/referral-program/> Showroom located at: 149 E Main St. Grass Valley, CA 95945 _______________________________________________ List sponsored by Redwood Alliance List Address: [email protected]<mailto:[email protected]> Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm<http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org<http://www.members.re-wrenches.org>
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