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Original question:

TMS320F28027F: how to make Dead time distortion correction

TMS320F28027F: dead time compensation

Dave Hunson
Expert 1760 points

Part Number: TMS320F28027F
Other Parts Discussed in Thread: CONTROLSUITE

Hi dear Luo.

1. Install  ControlSUITE https://www.ti.com/tool/controlsuite

2. Find the example project at the folder C:\ti\controlSUITE\development_kits\HVMotorCtrl+PfcKit_v2.1\HVPM_eSensorles

3. Find the code below in the project.

dbc1.scale = _IQdiv(_IQdiv2(pwm1.Deadband), dbc1.Ith); // uncomment to tune in debug
dbc1.Kdtc = _IQmpy(dbc1.scale, dbc1.gain); // uncomment to tune " "
PWMwDBC_MACRO(1,2,3,pwm1,clarke1,dbc1);

I analyzed the code  I have a question

for compensating dead band we have to add or substract ( DT/2) but I saw in "HVPM_eSensorles " we have a.  dbc1.gain  = _IQ(0.5); 

so we add and substract (DT/4)         ( (deadband/2)*0.5)

why is that would you please explain about it?

thanks for attention.

Dave.

  • +1
    TI__Mastermind 27240 points

    For the motor we tested, anything more than DT/4 was injecting even more noise. Probably because of the quality of current sensing, and again it may be due to the noise picked up in the feedback - may be layout issue. Your observation in right though, for your test setup, you can try DT/2. What we have shown is just a platform set up and not necessarily the final one. Hope it helps.

  • 0 in reply to Ramesh Ramamoorthy
    Expert 1760 points

    Sure dear Ramesh It DID helped!

    I have one more question,

    I am using ACIM (3kw~45kw)  600VDC bus ,now my case is (3kw ACIM 1500RPM with dead band compensation )so, when motor no loaded, Motor not spin circularly I mean the speed of motor in every rotating is not  linear ,and it has vibration and oscillation. and current of motor change from (1 to 6A) with no load. this  vibration and oscillation  will intense in some RPM range (from 900RMP to 1400RPM).

    BTW, when motor on the load I can not feel motor oscillation!!!

    But in some application such as elevator motor must spin with out vibration .because some times motor is not loaded.

    I saw a lot  VFD's that don't have this problems,

    Dear Ramesh , this problem is with me for more than 10 years I tried to solve it completely but I couldn't Disappointed.

    Should I change the "dbc1.gain" in some RPMs ?

    Or any other method should I look for?

    Thanks for your Attention.

    Dave. 

  • 0 in reply to Dave Hunson
    TI__Mastermind 27240 points

    There are voltage based methods, and we may release that example later this year. Suggest to do some web search for literature on that.