Diode Required for 120VAC Circuit

Discussion in 'The Projects Forum' started by ajthomson, Apr 14, 2011.

  1. ajthomson

    Thread Starter New Member

    Apr 14, 2011
    1
    0
    Please help if anyone can.

    Is it possible to supply a single load (1/3 hp motor) with 2 separate 120VAC supplies without the supplies feeding into each other by using diodes...and how ?

    Supply 1 has the starting capability but will not be used for running...Supply 2 has the running capability but not able to start the motor...

     
  2. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    I think it would behoove you to give far more information than what you posted. As it stands now, with the information that you provided, a diode will not fulfill your requirements.
     
  3. AlexR

    Well-Known Member

    Jan 16, 2008
    735
    54
    If the motor is a AC motor then the answer is a definite NO! If it is a DC motor then you could possibly do it but without a lot more information we can't make any meaningful suggestions.
     
  4. CDRIVE

    Senior Member

    Jul 1, 2008
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    By the way, I won't be so bold as to say that this will happen with all AC motors but for many that I played with many years ago, putting a diode in series with them acted like a brake.
     
  5. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    A curious problem. It sounds like you're trying to do what the Start-Run windings do in some AC motors. I think you would need a relay to switch from one AC supply to another.
    But...can you give us the big picture?

    Ken
     
  6. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
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    Yes, and he would need a current sense circuit to detect when the start winding has switched out. Then he would probably need a zero crossing detector to minimize transients.
    This whole thing is really goofy. Makes more sense to just get a supply that will do the job.
     
  7. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    If one of the supplies has enough power to start the motor, it has enough to keep it running. Agree that the entire concept seems rather goofy.
     
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