[RE-wrenches] Step-up/Step-down Transformer question

Tue Sep 18 21:34:14 EDT 2018

Currently up in the air as to whether 2020 will allow that on 1- and 2- family houses. If so then yes...currently don’t know of any. 

Brian

> On Sep 18, 2018, at 2:45 PM, Jay <jay.peltz at gmail.com> wrote:
> 
> Does anyone make a 1000vdc single phase inverter?
> Would reduce wire costs dramatically 
> 
> Jay
> Peltz power. 
> 
>> On Sep 18, 2018, at 11:36 AM, Lorenzo Ortiz <lorenzo at cal-solar.com> wrote:
>> 
>> Thanks for all the input guys.  After looking at the 3 phase with transformer options with some transformer manufacturers, that has been pretty much ruled out due to complexity/cost. 
>> With single phase step-up and step-down transformers, even at 600VAC, it still requires some monster wire.
>> The best solution seems to be placing the inverters next to the POI and just running long strings from the array back to the inverters and accepting up to 4%-5% voltage drop. And that's with #8 instead of the usual #10 AND accounting for worst-case production.
>> 
>> Man, sometimes this solar stuff is just crazy...
>> 
>>> On Tue, Sep 18, 2018 at 10:15 AM, Blake Gleason <blake at sunlightandpower.com> wrote:
>>> Good advice already on this thread.  A couple of points to consider:
>>> 
>>> 1. Re: step-up/step-down option (probably what I'd do): definitely pay attention to transformer spec to minimize both magnetization and operating losses.  Newer DOE 2016-compliant transformers are MUCH better than before, and that's just the minimum standard.  If you really want to minimize magnetization losses, you can always design a relay/timer to disconnect the transformers at night (from the interconnection side), although I've found that this setup is either very expensive or too unreliable (nuisance tripping upon re-connect, timer gets "off" cycle somehow, etc).
>>> 
>>> 2. I think someone mentioned a 480V single-phase inverter.  I'm not aware of a high-quality product meeting that description.  Is there one?  All of the "480V" single-phase inverters I'm aware of are 277V (line to neutral), which is hardly worth the transformer effort (versus 240V).
>>> 
>>> 3. Definitely use aluminum wire for the long run.  If wire size is still too large, even with step up/down tranformers, consider allowing slightly increased voltage drop at full power (say, 5%), and, depending on typical grid voltage at the site, change taps on one of the transformers to err on the low side (from inverters' point-of-view), to keep the inverters from tripping at upper voltage limit at full power (max voltage drop/rise).
>>> 
>>> 
>>> Blake
>>> 
>>>> On Tue, Sep 18, 2018 at 9:57 AM, Jerry Shafer <jerrysgarage01 at gmail.com> wrote:
>>>> Lorenzo
>>>> You might want to look at relocating the inverter(s) closer to the meter instead of the array, one reason is even if there is some line loss at full power its less as the voltage goes up and the inverter does not see the line resistance that can cause high voltage issues at the inverter. Some engineers use more side of peak performance than full power, this keeps wite size down and does not effect output
>>>> Jerry
>>>> 
>>>> On Sep 17, 2018 9:42 AM, "Lorenzo Ortiz" <lorenzo at cal-solar.com> 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
>>>> 
>>>>     loren at cal-solar.com  (530) 274-3671
>>>>   
>>>> 
>>>> 
>>>> 
>>>> Showroom located at: 149 E Main St. Grass Valley, CA 95945
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>>> 
>>> 
>>> 
>>> -- 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>>                                      	
>>>                                      	
>>>                                     	
>>>                                      	
>>>                                      	
>>>                                      	
>>>                                      
>>> Blake Gleason - PE, LEED AP
>>> Director of Innovation & Technical Excellence
>>> 
>>> P: 510.845.2997 x128 
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>>> 
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>> 
>> 
>> 
>> -- 
>> Loren Ortiz   Commercial PV Designer
>> 
>>     loren at cal-solar.com  (530) 274-3671
>>   
>> 
>> 
>> 
>> Showroom located at: 149 E Main St. Grass Valley, CA 95945
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