Paralleling of 2 Large Voltage Stabilising Transformers

Discussion in 'The Projects Forum' started by ChiefEngineer, Jul 28, 2014.

  1. ChiefEngineer

    Thread Starter New Member

    Jul 28, 2014
    Good day All!!:confused:
    I am sitting with a problem, I am the chief engineer on board a 164foot super yacht and I have 2 x 50kVA 3ph 385VAC 50hz inverter/frequency drives which work together as a master and slave and each has its own voltage stabilising transformer. Both inverters are always on and in phase with each other and load share as the demand of the boat increases or decreases.
    The units are both ATLAS ShorPOWER CLASSICS and operate on any input frequency (50hz or 60hz) and can't take 110Vac 230Vac single phase or 380Vac - 500Vac 2 phase. There is internal DC BUS in each frequency drive and the two units set output to 385Vac 50hz so that the boat can have power where ever it dock in the world. Currently docked in country where shore power is 400V 50hz.
    Both Frequency drives have suffered damage as they are old and I need to get the boat off the massive on board generators onto dock power while we wait for engineers to fly in.
    Can I simply disconnect the frequency drives outputs before the voltage stabilising transformers and connect the dock side power to the transformers in a parallel connection????
    Phase rotation will be checked before final connections are made.
  2. ChiefEngineer

    Thread Starter New Member

    Jul 28, 2014
    please note that I made a typo, the line that states "and can't take 110Vac 230Vac single ...." should rad as follows: "and CAN take 110Vac 230Vac single...."
    Regards Chief Engineer
  3. crutschow


    Mar 14, 2008
    I see no problem with connecting the inputs of the two transformers in parallel as long as the transformers are rated for the voltage and frequency of the input power.
  4. inwo

    Well-Known Member

    Nov 7, 2013
    Not sure I follow.
    Inverters can take 110 on input, yet inverters output 385V.
    And transformers are on the output.

    Am I missing something.
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    I thought Dubai was 230V 50Hz? Anyway, 400V doesn't seem to meet your stated input spec unless it's 2-phase.
  6. inwo

    Well-Known Member

    Nov 7, 2013
    It would make more sense to me if multi-tap transformers were used on the input side.

    Inverters then used to output standard hz.

    Unless the inverters are inverter/transformers that can input wide range of 110-400VAC, 1-2-3 phase/50/60hz.

    Then I'm not sure of the purpose of output transformers.
    Are they Sola type.
  7. Johann

    AAC Fanatic!

    Nov 27, 2006
    As I understand it, the two inverter drives only condition whatever input supply is available and the two transformers are for isolation purposes. Also, if I read correctly, the transformers need 385V at 50 hz (from the output of the inverters). Now you are in luck, because your shore supply is 3-phase 400V. You can safely connect to your transformers (which you will first connect in parallel and identically phased).