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Electric Motors

  1. Nov 10, 2004 #1
    Can anyone tell me what is the simpliest and cheapest method to control of velocity of an electric motor?
    or what kind of motor to use to reach such a control?
  2. jcsd
  3. Nov 10, 2004 #2


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    Science Advisor

    Pick 2 of 3: Simple, cheap, effective

    A permanent magnet DC motor with brushes is a good choice for motor type.

    A resistor is simple and cheap but difficult to control because the power falls off exponentially as you increase the resistance. A variable resistor like a rheostat/potentiometer would allow you to control it over a range.

    A switching circuit would be the most effective (especially with feedback) but this is not as simple nor cheap as a resistor. By using the concept of PWM (Pulse Width Modulation) and sending pulses of certain lengths to the motor the circuit can control the average amount of current in the coils and thus control the speed/power much more effectively.

  4. Nov 10, 2004 #3
    You could also try using a variable voltage power supply on the motor.

    As long as it can handle the maximum necessary current at the highest voltage rating for the motor, it should work just fine.

    Here's a bunch of useful circuits.

  5. Nov 26, 2004 #4
    to control the speed of electric motor is a frequency inverter...it may not be the cheaper but it is more reliable and easy to use......
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