ATS - Auto Transfer Switch help

Discussion in 'General Electronics Chat' started by sfaizan, Aug 22, 2011.

  1. sfaizan

    Thread Starter New Member

    Aug 21, 2011
    2
    0
    I just built my Genset 25kva (3 phase 400V) (NG), need to setup an ATS system with 3 phase using contactors. I think I need to use 2 x 2 pole contactors for 4 wire 3 phase.
    Here's what I need,

    3 phase (4 pole) Auto Transfer swith (230 volts per phase 50Hz, 400V 3 Phase System)
    ------------------------------------------------------------------------------------


    1. Genset Auto start if Main grid is de-energized for say 30ses

    2. Switch from main to Generator Backup power when stable power receives from Genset.

    3. When main power is back, lets say stable for 10 ses then first transfer back to main and then send stop signal to generator.

    4. Also need one more option if Generator fails to start switch back to main power and do nothing.

    5. Generator is on NG (Natural Gas) so it sometimes need longer self to start. Like 5 to 10 secs



    I will be very gratefull if anyone help me with complete diagram and parts list.

    P.S we dont have readymade ATS pannels available in our country.
     
  2. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    Requirement 4 and 5 are unnecessary as Requirement 2 already mandate the fulfilment of 4 and 5. The switching will not be carried out if the Genset do not startup properly.
     
  3. sfaizan

    Thread Starter New Member

    Aug 21, 2011
    2
    0
    hmm ok Chung, so any rough idea or schematic where to start with. I am thinking to use 3 pole double throw contactors if I unable to get readymade transfer switch.
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    Or you could use two 3pole single throw. You will allso need 6 small transformers to safely measure the phase voltages and some battery backup to operate the electronics when no power is available.
    Two 555s and few diodes will do the timing job.
     
  5. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    25Kva at 400V three phase is a lot of power.

    Generally people do not build DIY transfer switch for such power but go for ready made transfer switch instead. There are just too many aspects at stake with a poorly designed transfer switch.

    I would not attempt to build it myself as I would properly ends up having one costing as much as a ready built one and not as reliable.
     
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