How to switch the ac phase not the neutral

Discussion in 'The Projects Forum' started by Mostafa Elhabrok, Nov 5, 2015.

  1. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
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    i have a single phase ac motor, and i have 3 apartments each one uses a different phase.
    i want to run this motor from every apartment by standard switch.
    the problem if two switches are closed at the same time, i have two phases shorten .
    i wanted to use a triac but i realized that it controls the neutral side (because of the common ground and using the gate )
    i want to control the PHASE side of each phase of the three.
     
  2. BR-549

    Well-Known Member

    Sep 22, 2013
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    “i want to run this motor from every apartment by standard switch.”

    Do you need to ONLY activate the motor from each apartment by chance?.......just turn on?

    Or do you need complete, separate control from each apartment?
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    The disadvantage of using a triac (or SSR with a triac output stage) is that it can fail either open circuit or short circuit. If the latter, then you could have two phases shorted. Can you arrange to power the motor from only one phase, but use the switches just to provide input signals to a controller for the motor?
     
  4. recklessrog

    Member

    May 23, 2013
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    I would be safer to use relays as there is less chance of them failing short circuit like semiconductors can. All you need then is to have a simple Phase monitor control that senses whether there is power to the motor and will not allow another phase to be turned on until the others are off.
    We controlled 4.5kV 6 phase windings on massive motors like that back in the late 60's early 70's.
     
  5. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
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    every apartment has its switch, what i need is that every apartment is able to run the motor from its phase without two phases shorten.
    as if two switches are closed at the same time that will be a short circuit between different phases
     
  6. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
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    that is a good idea but i did not prefer relays as they are slower , and depend on mechanical parts
     
  7. BR-549

    Well-Known Member

    Sep 22, 2013
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    What is the motor doing for these apartments?
     
  8. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
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    the problem is that the motor is running alot , and every apartment its own power meter ( cost )
     
  9. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
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    it is a water motor (pump)
     
  10. BR-549

    Well-Known Member

    Sep 22, 2013
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    What prevents apartment #1 and apartment #3 from drawing water, when apartment #2 has the pump on?
     
  11. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
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    the pump provides water for the three whatever any apartment turned it on
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If you want each apartment to pay their individual cost, what happens if the demand is from 2 or 3 apartments and the same motor is used?
    Max.
     
  13. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
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    if there is any way to control which phase is connected to the motor
    sorry i do not understand what do you mean
     
  14. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
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    i appreciate everyone's help
    but on my condition is there any digital way to control the 3 phases as the following
    when
    apartment #1 closes its switch then its phase is connected to the motor while the other two phases are disconnected
    and #2 and #3 like the same
     
  15. BR-549

    Well-Known Member

    Sep 22, 2013
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    So, whoever has the switch on......pays for everyone's water.

    I don't think I can help on this one.
     
    Mostafa Elhabrok likes this.
  16. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
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    not like that whoever has the switch on his phase is only connected and he pays his (ELECTRICAL COST) NOT WATER COST
     
  17. BR-549

    Well-Known Member

    Sep 22, 2013
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    Watermeters.
     
  18. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
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    no i dont care of this
    what i care is energy meter
     
  19. Mostafa Elhabrok

    Thread Starter New Member

    Nov 5, 2015
    11
    0
    is there any digital way to control the 3 phases as the following
    when
    apartment #1 closes its switch then its phase is connected to the motor while the other two phases are disconnected
    and #2 and #3 like the same
     
  20. BR-549

    Well-Known Member

    Sep 22, 2013
    1,981
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    Pump cost divided by the 3 water meters proportionally, is the only fair way, for your setup.
     
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