ac to dc motor

Discussion in 'The Projects Forum' started by floomdoggle, Oct 31, 2008.

  1. floomdoggle

    Thread Starter Senior Member

    Sep 1, 2008
    217
    2
    Hi all,
    I have gotten hold of an AC magnet motor. I am wondering if it could be run as a DC motor.. The reason is, when this motor is spun by hand, 12 volts come out. So, as a motor/generator on something like an electric bicycle it would be useful.
    With all thanks,
    Dan
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You mean that the rotor is built of a magnet? If yes the answer is no.
     
  3. floomdoggle

    Thread Starter Senior Member

    Sep 1, 2008
    217
    2
    Yes, the rotor has definite N/S poles, So, if no to DC operation, how about some type of hybrid? Like a DC pulse? And why not? Not to be an A--, just do not understand why.
    Dan
     
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You can approximate a sine wave by PWM to drive the motor (if you know how to do it and its not easy) but there are ready devices on the market called inverters which make this job.
     
  5. floomdoggle

    Thread Starter Senior Member

    Sep 1, 2008
    217
    2
    Hey mik3,
    Yes, very well acquainted with inverters, and thank you for the response. I would be glad to have some knowledge as to why this motor is so foreign to straight DC operation. And, yes, I have done much research on inverting AC to DC motors. I do run into a wall when sine wave inverters are mentioned.
    Dan
     
  6. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    The magnet rotor to rotate needs a rotating field around it which is created by the stator. This field can be created only with AC voltages which are out of phase, in the case of a 3-phase system, or by a single phase with the help of a capacitor. If you apply a DC voltage the field will be stationary and also you will burn the stator windings. Some motors can operate with both AC and DC voltages and are called universal motors.
     
  7. floomdoggle

    Thread Starter Senior Member

    Sep 1, 2008
    217
    2
    Thanks for the explanation. That makes sense. Iguess I'll just use it as a generator.
    Dan
     
  8. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    Note that it will be an AC generator.
     
  9. floomdoggle

    Thread Starter Senior Member

    Sep 1, 2008
    217
    2
    So, which of the three leads do I use for output? Or all three?
    Dan
     
  10. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Is it a single phase motor?
     
  11. floomdoggle

    Thread Starter Senior Member

    Sep 1, 2008
    217
    2
    I believe so. Three leads, capacitor between two leads. All leads in any configuration read 0 ohms on my meter. Thanks again for tyhe help.
    Dan
     
  12. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Use the red and yellow wires which are the run winding of the motor. You can use also the red-blue wires but the internal resistance of the winding is greater. Remove the capacitor.
     
  13. floomdoggle

    Thread Starter Senior Member

    Sep 1, 2008
    217
    2
    Thanks again
    Dan
     
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