Page 1 of 3 123 LastLast
Results 1 to 10 of 24

Thread: Inverter Running at 66% or Transformer

  1. #1
    Join Date
    Jul 2017
    Location
    Chico, CA, USA
    Posts
    19

    Inverter Running at 66% or Transformer

    Hello,

    Inverter Dilemma.

    Is it better to run 21kW on an SMA 30K or

    Run 21K on a SMA 20K with a 480Delta to 480/277 WYE transformer?

    The Transformer runs about $1,700

    Thoughts?

  2. #2
    Join Date
    Mar 2017
    Location
    East Coast
    Posts
    10
    Um. What?

    You're going to need to outline the situation a bit (much) better than this.

  3. #3
    Join Date
    Jun 2004
    Location
    Cherry Valley NY, Seattle, WA
    Posts
    4,213
    Pretty vague on the details. Let me take a guess at filling in the gaps. Do you have a delta service? Since the 30k is the only one that will do delta you are wondering about just going with the oversized inverter for simplicity? I see no disadvantage in an oversized inverter. What is the cost difference?
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  4. #4
    Join Date
    Dec 2012
    Location
    Placerville, CA, USA
    Posts
    19,130
    Quote Originally Posted by electrofelon View Post
    Pretty vague on the details. Let me take a guess at filling in the gaps. Do you have a delta service? Since the 30k is the only one that will do delta you are wondering about just going with the oversized inverter for simplicity? I see no disadvantage in an oversized inverter. What is the cost difference?
    It seems to me that the STP20000TL-US is in fact a three phase inverter, just with a different output voltage range spec. Which leads to the OP's question of whether that model with a transformer would still be more efficient or more cost effective than a partially loaded 30K model that would not need a transformer.
    As you note the 30K can connect either to 480Y/277 or 480 delta, while the lower power models require the 480Y/277 with neutral. I am sure the 30K's initial cost is higher than the 20K.

  5. #5
    Join Date
    May 2011
    Posts
    4,123
    From the customer's point of view, the larger inverter would be better since there will be no clipping and no transformer losses. Unless the transformer saved my company a lot of money I'd probably go with the larger inverter. Don't forget to include a bit of extra labor and material, and possibly additional overcurrent protection in the cost for the transfomer. Double check there's no start voltage issue with the larger inverter.

  6. #6
    Join Date
    May 2011
    Posts
    4,123
    Quote Originally Posted by GoldDigger View Post
    ... I am sure the 30K's initial cost is higher than the 20K.
    Yes, but probably in the difference is in the neighborhood of that transformer cost, depending on what pricing they're getting.

  7. #7
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
    Posts
    9,282
    Quote Originally Posted by jaggedben View Post
    From the customer's point of view, the larger inverter would be better since there will be no clipping and no transformer losses.
    FWIW and IMO, a 20kW inverter running with 21kW STC DC of modules is unlikely ever to clip.

  8. #8
    Join Date
    Jun 2004
    Location
    Cherry Valley NY, Seattle, WA
    Posts
    4,213
    To elaborate on what JB said, dont just think of the transformer cost, but also the labor and balance of system components. If it's not an auto, you need a GEC which can be a hassle for a rooftop system. We had to do a bunch of transformers on a rooftop system and it was super time consuming.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  9. #9
    Join Date
    May 2011
    Posts
    4,123
    Quote Originally Posted by ggunn View Post
    FWIW and IMO, a 20kW inverter running with 21kW STC DC of modules is unlikely ever to clip.
    I know, but on a 30kW inverter it definitely never will!

  10. #10
    Join Date
    Nov 2015
    Location
    CA, USA
    Posts
    517
    From a production point of view it's probably a wash, so look at the relative cost and choose. You can do a simulation of both in SAM but I feel they would come out about the same.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •