How a AC motor can reverse rotation with wire flips?

Discussion in 'General Electronics Chat' started by AlexLPD, Feb 13, 2015.

  1. AlexLPD

    Thread Starter Member

    Aug 22, 2010
    21
    1
    Hi to you all!

    When I was in highschool in the electricity shop tall us the rotation of an AC motor cant be reversed.
    Today we gave mainance to an AC 110-220V motor and in the plate has the legend; for changue rotation changue black wire to blue.

    Of course nothing to do with changing the color of the conductor. Just their position in the electrical joints.

    Latter on we have to changue rotation.

    And I'm guess whath is the theory behind this?

    From the rotation part... I guess the 110-220 has to do with the resistance of windings .

    Thanks.
    -Alex.
     
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  2. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    AC motors always have an imbalance in their magnetic fields or they wouldn't know which way to turn. Moving a couple of wires moves the imbalance.
     
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  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    AC motor is a vague description, there are several technologies, but simplistically all that has to be done is change the relative polarity of a a field, whether induction, Universal, synchronous, split phase, 3 phase etc.
    Max.
     
    Last edited: Feb 13, 2015
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  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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  5. AlexLPD

    Thread Starter Member

    Aug 22, 2010
    21
    1
    So in resume...
    All AC motor.can be reversed, and for doing that it is necessary to flip the pole of the start winding.

    Concreatly in AC motor....
    At changue the wires we are fisically changing the start pole? At the same phase?.

    So lets say the ph1 is the start and goes to 9 o clock. By changing the wires... We are putting the PH1 to 3o clock for saying? (I now may be a little more close to impulse the cage)

    Alex.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    In a 1ph induction motor a method is used to create an artificial phase (split phase) usually done using a second winding in series with a capacitor to shift the phase ~90°.
    reversing either of the windings results in a motor reversal, or a relative phase angle change between the windings.
    Max.
     
  7. AlexLPD

    Thread Starter Member

    Aug 22, 2010
    21
    1
    So... Can I reverse the polarity of this fans with the appropriated arduino sketch and the appropiatted circuit?
    [​IMG]
    Maybe a pass by cero triacs and a squematic to allow the changue of the start?

    These are 115V AC, capacitor start fan motors... they run on 0.2Amp

    Excuse the trouble but... can share an schematic? .
    They will not be changing the rotation very often, just a litte bit of a trick.


    Thanks a lot.
    -Alex
     
  8. AlexLPD

    Thread Starter Member

    Aug 22, 2010
    21
    1
    Well 5 min of free time;

    http://lumberjocks.com/topics/48372
    How to reverse turn on a sander.

    Know I have to take a closer look to the motor, and see if have the leads prepared or need to be added from ouside.
    I guess a simple 3 position switch will do the trick. And once it passed on the arduino control Tada... reversible
    air flow on evap...

    I know I know the Q inst gone be the same, and all... but for this particular application come handy dandy.

    Thanks a lot!
    This is a great place to learn stuff.

    -Alex.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You will either need to access both ends of both windings, or if as often the case with a small fan motor, the start and run windings may be identical, accurately measure the resistance should indicate it.
    If so see the pic for the dashed alternate connection, this method uses the existing 3 wire connection and just swaps the winding for main and split phase. (run/start).
    Max.
    [​IMG]
    Max.
     
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  10. AlexLPD

    Thread Starter Member

    Aug 22, 2010
    21
    1
    So... Can I reverse the polarity of this fans with the appropriated arduino sketch and the appropiatted circuit?

    Maybe a pass by cero triacs and a squematic to allow the changue of the start?

    Thanks a lot.
    -Alex
     
  11. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    In post #1 you said you can reverse the motors by moving a black wire and a blue wire.
    We can not see the drawing on the motor from here.
    Nobody can draw for you how to wire an Arduino without knowing WHERE to move the wires.
     
  12. AlexLPD

    Thread Starter Member

    Aug 22, 2010
    21
    1
    Hi, yes! ... the wiring and the coding of the arduino will be no problem... Once I add the neccessary leads to the motors, the circuit is pretty easy, and control it by an arduino is also easy.

    Thanks!
    -Alex.
     
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