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Facing problem in FOC for IM.

Amtech
Genius 4585 points

Other Parts Discussed in Thread: TMS320F28069F

Dear all,

I am using TMS320F28069F controller and motorware13 example implementation in my custom board for AC induction motor 415V/50Hz system. My motor data are 415V, 50Hz, 2900Rpm, 13.3Amp, 2Pole, 7.5kW and motor taking 3.9Amps in no load condition (no load on shaft).

I face below two problem.

  1. When motor running in 10Hz, it will take 3.9Amps and motor running Ok, but when I set 1.00Hz, motor running in force angle and it's current increasing up to 13.3Amps. I cant understand why this happen?

  2. If I set 10.0hz(600rpm) Ref frequency, Acceleration time is 2Sec and I enable gMotorVars.Flag_Run_Identify = 1 than output frequency can not smoothly accelerate. It will take some jerk in starting. I think In starting Output frequency uncontrolled and after that it will controlled.

Is any one know about this type issue?

  • 0
    TI__Guru** 119680 points

    1. disable force angle. force angle should never be used when trying to run at a speed.  ForceAngle's only purpose is to help generate a rotating stator field that allows the motor to move enough so that FAST can lock on to the rotor angle.  It is mostly used for first start-up, but this is application dependent. IF you use it for start-up you should immediately disable in nearly all cases.  Also, for start-up you should insure that

    USER_FORCE_ANGLE_FREQ_Hz > 2 * USER_ZEROSPEEDLIMIT * USER_IQ_FULL_SCALE_FREQ_Hz

    this makes a big difference in start-up capability / repeatability. 

    This value

    USER_ZEROSPEEDLIMIT * USER_IQ_FULL_SCALE_FREQ_Hz

    will be dependent on the motor flux in relationship to the ADC_VOLTAGE.  You need to find a value where FAST works pretty well, then make sure that the FORCE_ANGLE_FREQ is 2x greater.

    2. I assume you mean for initial start-up?  The initial rotor angle is unknown, so the initial accutation of the system may not produce enough torque to start the acceleration, so when enough torque is created it may not be so smooth.  There are several methods discussed in SPRUHJ1 to help with this topic.  RsRecal (or any injection of +Id current) is a good method.  Also important is the tuning of the speed controller.  It may just be as simple as making sure yours is aggressive enough to generate enough initial torque.  This is an area where InstaSPIN-MOTION and the SpinTAC controller is a significant improvement.  It helps with start-up and especially velocity transitions through zero speed.  It is very challenging to get a stiff enough torque request from a PI controller as you travel through zero speed, but we can do this quite easily with SpinTAC.  Considering you are already using a 69F, I would highly recommend using a 6xM version for this capability. It is superior.