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?

 

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.

 

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.

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

 

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

 

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.

 

I am a bit thick, where did you get your "154 volts DC"? Is this the calculated mean of a 1/2 sine wave?

RMS for half-wave rectifier = 200*1.414/2.

 

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.

why dont use capacitor filter?
if dont the rectifier output is ripple and doesent stable and smooth