BLDC motor couldn't start itself ???

Discussion in 'General Electronics Chat' started by kim_taeyeon, Sep 13, 2011.

  1. kim_taeyeon

    Thread Starter New Member

    Aug 24, 2011
    Dear all

    I have been working on a project related to BLDC Motor. I am using a micro-controller, a three half bridge inverts and a BLDC motor.

    I have finished the code of generating pwm signals feeding into the bridge inverter. The problem is that, I powered up the bridge circuit with +20V, the motor can not start itself. I had to flip my finger onto the rotor, kind of like giving an starting inertia, to make it rotating either CW or CCW.

    I am really stuck on this problem and would anybody suggest me something that causes this problem?

  2. SgtWookie


    Jul 17, 2007
    With no schematics or code shown, it'll be rather difficult to determine what the problem is.

    However, perhaps you are trying to give the motor essentially 3-phase power at too high a frequency for when the motor is stalled, and it won't overcome the stiction. If that's the case, try ramping up the 3 phases slowly, so the motor has a chance to overcome stiction and inertia.
  3. shortbus

    AAC Fanatic!

    Sep 30, 2009
    You make no mention of 'Hall effect sensors' in your post. These are used to give the motor driver feed back to tell it which winding in the motor needs to be activated. How are you determining what winding is turned on?
  4. kim_taeyeon

    Thread Starter New Member

    Aug 24, 2011
    I definitely use 3 hall sensor signals feeding back to the micro-controller and I have done the coding to determine the sequence.
  5. eblc1388

    Senior Member

    Nov 28, 2008
    When the rotor is not rotating, I don't know if the hall sensor signals are helpful or not.

    Have a look at the ST application note AN1276 regarding BLDC rotor pre-positioning which moves the rotor to a particular known position and then you can begin the turning sequence via software control.
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Please describe your motor start procedure.