Maintain v/f ratio in pic microcontroller output

Discussion in 'General Electronics Chat' started by innovetion, Feb 3, 2016.

  1. innovetion

    Thread Starter New Member

    Oct 16, 2015
    4
    0
    Hello,

    I am using PIC18f4550. My aim is to control AC induction motor. For that I have generated required PWM pulses for required frequencies. But I need to maintain V/F ratio at the output. Which I am unable to do.

    Please suggest me.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,018
    3,235
    The PMW modulation frequency determines the AC frequency applied to the motor, and the PWM duty-cycle along with the PWM carrier voltage determines the AC voltage applied to the motor.
    So from the modulation frequency you calculate the needed duty-cycle to get the desired motor voltage for the PWM carrier voltage you are using.
     
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  3. innovetion

    Thread Starter New Member

    Oct 16, 2015
    4
    0
    Thanks crutschow.
    Can you please explain briefly ?
     
  4. dannyf

    Well-Known Member

    Sep 13, 2015
    1,819
    362
    Change the period register and maintain 50 percent duty cycle.

    Better use a v/f converter or a pic with NCO.

    If the frequency isn't too fast, consider dds in software.
     
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