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Thread: No load losses - normal vs reverse fed

  1. #131
    Join Date
    Apr 2008
    Ann Arbor, Michigan
    170122-1007 EST

    Phil Corso:
    I ignored "shellac" because it did not apply to the A41 transformer which is only about 20 years old.

    Besides a core material difference between the two transformers there is going to be a great difference in the wire insulation temperature capability. This would be a big factor in the VA rating for what otherwise might seem to be almost the same core physical size.


  2. #132
    Join Date
    Jun 2004
    Cherry Valley NY, Seattle, WA
    I just did an experiment of my own. This is the system I mentioned earlier.

    To Recap: Transformer A, 15 kva encapsulated, 240/480 to 2400. Transformer B, 2400 to 120/240 15 KVA single bushing/MGN padmount. Transformer A is on the utility end, windings connected in parallel for 240V. I dont have a PT to use on the 2400 side, so I can only measure the 240V side and add/subract to get power measurements. No load loss when feeding A 240V is 130 watts. With transformer B connected, 190 watts total. I reverse fed the setup with a generator and got the exact same losses. The padmount is clearly quite efficient, using only 60 watts. But the Encapsulated is still way more efficient than the first transformers I used which were only 10 KVA and used 300 watts each. They were super old. The Olsun encapsulated is newer than 1993, thats all I know. The padmount was manufactured in 2009, FWIW.

    This works out to about $80 per year over if I used another padmount. I got this one for about $650 delivered, and that was the cheapest I have found them. I think Ill just plan on adding a few more panels to my PV system
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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