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Reversing Taifu QB70 single phase AC motor

  1. Sep 16, 2014 #1
    Hello Guys,

    I got a Taifu QB70 water pump. But no more in use, I wish to use this motor in a gate opener project of mine.

    However I cannot figure out how to make the motor rotate in a reverse direction.

    What I tried ?

    1. I reversed the position of the capacitor thinking it would provide reverse initial torque, in vain.
    2. I reversed the intake leads of the motor(keeping capacitor leads intact), in vain again.
    3. Changed the leads randomly (hoping it doesn't blows off LOL)... but in vain

    THE MOTOR CONTINUES TO ROTATE IN A SINGLE DIRECTION.

    Can someone help me making this motor work reversely (as well as forward also of course), use of external circuit with button or series of buttons is acceptable.
     
  2. jcsd
  3. Sep 16, 2014 #2

    Baluncore

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    A single phase induction motor with a phase shifting capacitor usually has three terminals connecting to two separate windings. One terminal is common to the two windings, that connects to neutral. The other two wires connect to the active, but one has the capacitor in series. The motor direction is determined by which of the two active lines has the series capacitor.
     
  4. Sep 18, 2014 #3
    @Baluncore ... Thanks a lot for the instructions. I got the motor rotating both sides now.

    However, On rotating forward (its original direction) it makes a light humming sound, something as "VMMMMMMmmmmmmm"

    But on getting it to work the reverse direction it makes a rather odd sound, something as "BRRRRRrrrrrrrr" (LOL).


    I want to know it it would be anyhow destructive to use the motor in the reverse direction ?
    NOTE: For my gate opener project i would need it to run backwards (pulling the gate) for about 30 to 40 seconds.
     
  5. Sep 18, 2014 #4

    Baluncore

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    With the motor disconnected from the power and capacitor, use a multimeter to measure the resistance between pairs of the three wires. Two of the values should sum to the third. The highest value will be between the two active outer ends.

    Are the two windings of the same resistance?
    Check that you have the middle wire connected to neutral.

    What does the motor sound like when it is turned by hand in either direction?
     
  6. Sep 18, 2014 #5
    Hi @Baluncore, when turned by hand (in either direction) the motor does not make any sound, only feels a bit stiff (may be because the motor is a bit rusty).
     
  7. Sep 18, 2014 #6
    Which switch allows this kind of flow ?

    Guys can somebody tell me what kind of switch I can use to accomplish the flow depicted in the attachement (Reverse.png) ?
     

    Attached Files:

  8. Sep 18, 2014 #7

    Baluncore

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    You have drawn a cross-over switch. Use a two pole, two position switch.

    But to reverse a motor you only need to use a single two position switch.
    Connect the capacitor between the two active terminals. Then distribute the active power to one side of the capacitor to go forwards or the other side to go backwards.
     

    Attached Files:

    Last edited: Sep 18, 2014
  9. Sep 18, 2014 #8

    NascentOxygen

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    Staff: Mentor

    Might this be what you are needing? One DPDT switch can reverse the way the two input wires connect to the pair of motor wires.

    012_02.gif
     
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