help converting a motor to run on AC

Discussion in 'The Projects Forum' started by wazeer, May 30, 2010.

  1. wazeer

    Thread Starter New Member

    May 30, 2010
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    Hello all, checking in with a project that I need help with.

    I am building a turn table to turn aluninum wheels on so that I may use a buffer to polish them. I need it to be a variable speed so I can start slow and finish up at a higher speed.

    Here are the specs on the motor I found:


    SPECIFICATIONS
    • Speed 250 RPM
    • Voltage 130 DC
    • Amperage 0.5 Amps
    • Power 1/12 HP
    • Torque 10 in - lbs.
    • Gear Ratio 10:1
    • Rotation Reversible
    I want to run this motor on 120 vac and need to be able to control the speed from 0 to 250 rpm. I have been studying on it and realize I need a full wave rectifier, however I am not sure what else I would need to complete this.


    I am curious how some of you would design this?


    Thanks in advance.
     
    Last edited: May 30, 2010
  2. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    At a half-amp, you would be better off building a 130V power supply to run it on what it's designed to use ... DC.
     
  3. wazeer

    Thread Starter New Member

    May 30, 2010
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    Ok, If you dont mind me asking, what would be involved in building that?
    From what I understand I will need a transformer that will take the 120 volts to 130 volts,
    then a full wave rectifier to change from ac to dc
    A potentiometer to adjust the voltage / change the speed
    I have read that a capacitor could be used to smooth out the voltage, however it may not be needed because it running a DC motor
     
    Last edited: May 31, 2010
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    It's best you PWM Drive it. It's what I am thinking of to drive my tread mill motor
     
  5. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    It appears your interest is in polishing aluminum wheels, not developing a motor control. I suggest you look at a low cost (<$100) commercial solution.

    Check out:

    http://www.driveswarehouse.com/Drives/AC+Drives/?gclid=CObQyOmo_KECFRdSagod3X-jDQ

    http://www.kbelectronics.com/catalog_chassis.htm

    Your 130 VDC motor is a bit odd, but maybe at such a low HP rating, it is not. Even with a 1:10 gear reduction, I wonder whether it will have enough power to rotate against the buffer. But then, that is another issue. Since the price difference between a 0.5 to 1 HP controller and a 1/12 to 1/6 controller ( if made) is probably pretty small, I would go with a slightly larger and possibly cheaper controller just in case you have to get a more powerful motor for the turntable.

    I have found ebay to be a relatively cheap source for DC motor controllers, once you have narrowed your choices. You will find new KB drives for less than $100 and used for $30 or so in the 1 HP and less range. As usual, beware of "removed from operating machinery, condition unknown" ads. That may mean that the machinery was just fine, it was the controller that started to smoke.

    John
     
  6. wazeer

    Thread Starter New Member

    May 30, 2010
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    Thanks for your replies. My interest is in building this turntable, but I am also interested in having something with a practical use. This is why I want to build as much of it as I can. I realize this motor might be a little undersized, however all it has to do is turn the wheel so I can polish the wheel evenly.

    I think the wheel, once up to speed, will act as a flywheel and help to keep the wheel spinning.
    If I could chuck it up in my lathe it would work perfectly.

    So if you guys think building a power supply is too hard or not practical, I will scrap the idea. If it is something that can be built, then I would really like to bo it.

    Can 120 vac operate this motor without using a step up transformer? If the transformer would make it operate better then I will go that route. If I understand it correctly, a full wave rectifier will operate the motor with out a smoothing capacitor.

    I really appreciate your guys replies, and I hope I am not being a nuisance.
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Without knowing what type of DC motor you have, one cannot say whether it will operate on AC. I suggest you read these links:

    http://en.wikipedia.org/wiki/Brushed_DC_Electric_Motor

    http://en.wikipedia.org/wiki/Universal_motor#Universal_motors_and_series_wound_DC_motors

    For the second link, scan down to the section on universal motors.

    Can you post a picture of the data plate for the motor? What was its originally intended use? Is the motor reversible (easily)? Does it have permanent magnets? These characteristics may give a clue as to whether it can run on AC. I suspect that if it has just a DC rating that it is not a universal motor.

    In any event, just hooking a bridge rectifier between the motor and the mains is a dangerous suggestion. Where did you get that idea? If the mains are 120V and you simply rectify it, the maximum rectified voltage will be more than 130 V DC.

    John
     
  8. wazeer

    Thread Starter New Member

    May 30, 2010
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    I have a speed controller that came out of a treadmill if you need one. It is a 90 volt dc motor
     
  9. wazeer

    Thread Starter New Member

    May 30, 2010
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  10. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    From the link given in post #9:

    It won't run on AC. As previously suggested, you need a real power supply -- not just a bridge across the mains. If you want variable speed, then PWM is the way to go.

    John
     
  11. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Based this on GE SCR Manual, 5th ed, 1972, fig 10.9. It is simple & if using NTE 5646 TRIAC, the DIAC is built in. Caps 300V, 100 ohm-1W, diodes 2A, 300V bridge or even 1N4004's.
     
    Last edited: Jun 1, 2010
  12. wazeer

    Thread Starter New Member

    May 30, 2010
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    Last edited: Jun 1, 2010
  13. wazeer

    Thread Starter New Member

    May 30, 2010
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    I just looked on fleabay and all the PWM's were for 12 to 40 volts. So you think that maybe I should look for another motor?

    I want something that will stay between 0 and 200 rpm. I assumed that DC was the only way to go. What about an AC motor. Does anyone know of an ac motor that will do this?

    Once again I really appreciate all the help
     
  14. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Or the PWM model KBWD-13, except for $$$. I would rather control a DC motor rather than AC.
     
  15. wazeer

    Thread Starter New Member

    May 30, 2010
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    I finally have made it back to this project. A coupla changes. I found a 90 volt DC gear drive motor It has more HP than the other motor I was looking at. Now for a coupla questions.

    I have a motor controller that came out of a treadmill which also had a 90 volt motor. Is a motor controller the same thing as a power supply?

    Providing the amperage draw is the same for both motors, Wouldn't this controller be all I need to run this motor?

    Lastly, the circuit has a 5.5 mh choke wired in series with the motor. Is this how the voltage is converted from AC to DC? I read where a choke is designed to block High frequency AC currents but allow lower frequency currents, DC, to pass. In laymans terms, what does this choke do?

    Thanks for everyones replies, I will eventually get this thing figured out.
     
  16. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    choke is to prevent or eliminate interference.
    it's not an AC to DC converter.

    Showing what u have will help
     
  17. wazeer

    Thread Starter New Member

    May 30, 2010
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  18. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    I said wht you have on hand.
    A pic of ur board will help better
     
  19. wazeer

    Thread Starter New Member

    May 30, 2010
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    here is a pic of the board I have. It is the same one that was on the link I posted
     
  20. wazeer

    Thread Starter New Member

    May 30, 2010
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    7

    So I'm guessing the choke was to stop interference from the motor to the digital display that was on the treadmill.
     
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