Point on wave switching

Discussion in 'The Projects Forum' started by Julius, Oct 9, 2006.

  1. Julius

    Thread Starter New Member

    Aug 10, 2006
    4
    0
    Hi! Everyone.

    I am doing a project on point on wave switching of an inductive load i.e. a transformer (220/110V; 275VA), begining with single phase but would like to import the solution to a three phase system and a higher rated transformer.

    I am attempting to prevent high in rusuh currents at the moment of energization. The optimal point of energizing the transformer assuming zero residual flux is at supply votage peak, at this point the induced current is at zero crossing. As a result, the transformer core does not saturate.

    I have considered using a light dimmer circuit to control the poinf of switching. The hurdle is that I will typically not supply full power to the tranformer.

    I also need to add a zero detector circuits, to be able to track voltage peak.

    I am struggling with intergration of the circuit. I would appreciate any advice or maybe a different approach to the project.

    Julius
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    It might be helpful to know the voltage and power rating of the transformer in question.
     
  3. Julius

    Thread Starter New Member

    Aug 10, 2006
    4
    0
    Hi! I apologise for that.

    It is a 220/110V; 275 MVA single phase transformer. I am hoping to duplicate the solution to a three phase system, with the necessary changes, and even use the solution for higher rated transformers.

    Julius
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,590
    777
    Are you really, really sure its 275 Mega VA at 220V? That´s something like 1250kA :eek:, and then there is no solution for your problem, beacuse there´s no DIY device on Earth that could safely switch such current, and of course it is not a solid-state relay or SCR.

    Even 275kVA seems quite high, and 275mVA is too low, so I can´t imagine what you meant. Maybe just 275VA?
     
  5. Julius

    Thread Starter New Member

    Aug 10, 2006
    4
    0
    Hi!

    Thanks Kubbek. Excuse my foolishness. It is 275VA.
     
  6. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    And that's how you do it.
    When you get the zero cross signal you only need to time 5ms for 50Hz (~4.2ms for 60Hz) to the peak - the actual time will be a bit shorter, due to your zero cross circuit needing to pass the zero (slightly) before it can react, but that will be a steady delay. A simple monoflop should do.
     
  7. Julius

    Thread Starter New Member

    Aug 10, 2006
    4
    0
    Thanks, but waht is a monoflop?
     
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