drive dc-motor with half wave or full-wave?

Discussion in 'General Electronics Chat' started by h.d, Feb 8, 2008.

  1. h.d

    Thread Starter Active Member

    Oct 22, 2007
    150
    0
    hi all
    i have project to drive dc-motor
    i will rectify the AC input(220V)
    the motor is 220dc 4500rpm ,but i dont need the whole speed
    so,if i use halfe-wave rectifier to get the dc the output will be 154Vdc
    which will give 300rpm (i dont need more)
    know is the using the half wave agood in reality or the full-wave is better
    also for the motor health?
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    50Hz is a pretty low frequency for PWM. I suspect the motor would vibrate mightily. Also, if this is for your treadmill project, a more conventional PWM would give the operator some control over belt speed.
     
  3. h.d

    Thread Starter Active Member

    Oct 22, 2007
    150
    0
    yes it for it;)

    i think that too
    in full bridge we get double frequency, which give the motor more stability
    and make speed control smoother.
    i think the vibration will ocuare in the low opperating voltages
     
  4. chuckey

    Well-Known Member

    Jun 4, 2007
    75
    10
    I am a bit thick, where did you get your "154 volts DC"? Is this the calculated mean of a 1/2 sine wave? One thing that is for certain is that due to the inductance of the motor windings you will get substantially less current flowing with 1/2 wave DC then with smoothed full wave. As said the motor will growl. It is importent to put a diode across the motor supply so any arcing of the brushes do not results in your rectifier being fried by back emf.
    Frank
     
  5. chand1

    New Member

    May 22, 2007
    3
    0
    Use full wave rectifier, but do not put any filter capacitor. Use a simple pwm circuit. You can limit the input control voltage to get whatever the maximum speed you want.
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    RMS for half-wave rectifier = 200*1.414/2.
     
  7. h.d

    Thread Starter Active Member

    Oct 22, 2007
    150
    0
    why dont use capacitor filter?
    if dont the rectifier output is ripple and doesent stable and smooth
     
Loading...