• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 30 subscribers
  • Views 685 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Starting PMSM without feedback with low frequency

Shahid Atiq
Intellectual 305 points

Hi dears

I have a PMSM with hall sensors. But i want to start machine without any feedback. I have read in CHAPMAN 's hand book about electric machinary that synchronous machines do not self start but we can start them by using low frequency during starting. So I am trying to start machine with 5 Hz from my invertor but machine just viberates and does not rotate. Phase sequence of Invertor voltages are exacctly same as that of back EMF of the machine that I measured by rotating the machine with another machine. 

Any suggestions about starting PMSM without feedback at low frequency and low power because high power may result in demagnetization of PMs incase of motor fail to rotate

Best Regards

 

  • 0
    TI__Mastermind 26065 points

    Hi Shahid

    5 Hz is not low enough to align the rotor with the flux for a PMSM which has strong magnetic rotor. The rotor will not comply the rolling magnetic field smoothly.

    You may apply a proper DC current, usually 20% to 50% of the working current rating to 2 of the 3 phases. After the aligning time, maybe several seconds, until the motor aligned and stopped with no vibration, then accelerate the rotation magnetic field (Sine wave or 180 degree controll is better for the accelerating) by commutation control starting from 0Hz to some level that the BEMF is easy to detected. Then, apply the sensorless BLDC control. You can refer to TI instaSPIN algorithm.

    Thanks.

  • 0 in reply to Wilson Zuo
    TI__Guru** 119560 points

    It is very difficult to do this unless you have a solid sensorless estimator which can start providing feedback at a low enough speed. With our InstaSPIN-FOC solution we have a ForceAngle.  This essentially replaces the sensorless estimator with a simulated estimation feedback of a rotor moving at a user configurablle set rotation speed.  This angle is used in the forward control (IPARK) with a standard Iq/Id PI torque control.  This method guarantees that you can produce a rotating stator field at a fixed frequency and potentially with maximum Iq (assuming your torque control is being commanded to max Iq), so it should rotate into a position to "catch" the rotor and produce a full torque start-up.

    The sooner you can move out of this ForceAngle and start using a true estimate of the rotor, the better.  That's why extremely good and stable estimators like FAST are so valuable in sensorless applications.

    The real question though is if you have hall sensors why aren't you using them?  They will give you a rough estimate of the rotor angle location to start...but you will still need to force some increment of this starting angle until you have better feedback (from an observer or your hall interpolation at higher speeds).