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Thread: Inverter sizing mystery

  1. #11
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    Quote Originally Posted by Dave A View Post
    Your 16 amp reading seems to be a sum of the current on all three phases.
    You multiply by 1.73 when you are using the current for one of the 3 phases ... (and this assumes a balanced load).

    .
    which is what it is 16amp on one phase and it is balanced as it is 4 escalators with 3 phase motors , each escalator drawing 8 amps per phase , confirmed with tong test

  2. #12
    Platinum Member Derlyn's Avatar
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    From the 8A per phase reading that you get for each motor, that calculates to 3.68Kw/ph multiply by 3 = 11Kw.

    Can you confirm if they are 11Kw motors ?

    Ooops !!! a 5.5Kw motor draws approx 7,5A.

    Can you confirm what size the motors are ?
    That will confirm if the AC readings obtained with the tong tester are correct.

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    Quote Originally Posted by Derlyn View Post
    From the 8A per phase reading that you get for each motor, that calculates to 3.68Kw/ph multiply by 3 = 11Kw.

    Can you confirm if they are 11Kw motors ?

    Ooops !!! a 5.5Kw motor draws approx 7,5A.

    Can you confirm what size the motors are ?
    That will confirm if the AC readings obtained with the tong tester are correct.
    Cant get to the motors - Have used 3 different tong testers in different makes as well and the logger - All 4 give the same readings
    Last edited by GCE; 10-Jul-24 at 03:56 PM.

  4. #14
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    These are 2 pics of the inverter screen running on grid in parallel
    On the load side under one with a tong tester I get 25amps and on the other 14 amps

    Attachment 8933
    Attachment 8934

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    Platinum Member Derlyn's Avatar
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    There are a million things going through my mind. So many questions.

    Are you any closer to solving the mystery ?

    Sounds as if there's power coming from somewhere else besides the batteries.

    If there were panels involved then one could understand it, but without panels, it is a mystery.

    Is the output of a 3ph inverter in a star or delta configuration?

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    No closer , have spoken to numerous people that are involved with designing including supply and always the same answer - Can't be possible

    Config would be star and there is nowhere else that power can be coming from

  7. #17
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    Still working on this "mystery".

    I dont know 3 phase inverters.
    Dave mentioned that a 12Kw 3phase inverter consists of 3 single phase 4Kw inverters.

    Now the question is, what is the phase voltage of each 4 Kw inverter ? 220v or 380v ?

  8. #18
    Platinum Member Derlyn's Avatar
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    I somehow don't think there's a problem with your physical current readings.

    The "mystery" is somewhere in the power calculation in my opinion. Now to find it.

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