Help!! Help to design Brushless DC motor driver!!!

Discussion in 'The Projects Forum' started by naren_iisc, Mar 8, 2015.

  1. naren_iisc

    Thread Starter New Member

    Jan 13, 2015
    21
    0
    Hi everyone,

    I have designed a BLDC driver for 24V, 300W BLDC hub motor using Allegro's A3931kjpt IC. my digital inputs are,
    PWM freq=20KHz
    DIR,COAST,MODE,ESF,BRAKE=1
    internal current control with Vref=3.5V
    Vdsth=3.5V.


    With this setup my motor runs from 0% to 100% duty cycle. But it is not able to provide the torque. Even at 100% duty cycle if I try to stop the motor, it stops.

    Can someone suggest me the solution?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,554
    2,375
    Either not receiving full voltage or the current limit circuit operating too soon?
    Max.
     
  3. Electronautilus

    New Member

    Mar 4, 2015
    12
    2
    Hello,

    From my understanding a BLDC will generate more torque when there is a larger amount of current applied.

    Heat loss (such as described in the link below), as well as physical size, play a role in the torque capabilities of a BLDC. Here's an informative link I found that may help you go in the right direction: http://www.edn.com/design/sensors/4...Part-I--Construction-and-Operating-Principles

    Sorry if this isn't what you're looking for, I hope the math on that page helps though!
     
  4. naren_iisc

    Thread Starter New Member

    Jan 13, 2015
    21
    0
    @MaxHeadRoom
    Thanks for reply. Voltage is not at all dropping. and current limit what I set is much grater than actual current motor is drawing from the supply.
    In my board I put Vref=4.5 which is current limit value. and my Rsense=10mOhm

    @Electronautilus
    Thanks, but yeah I knw this math, but i want help specific to this IC A3931.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,554
    2,375
    What is the configuration of your drivers?
    Max.
     
Loading...