TMS320F28379D: C2000™ microcontrollers forum

Kaarthi Chandrasekaran

Part Number: TMS320F28379D
Other Parts Discussed in Thread: DRV8323

Hi,

I am using a TMS320f28379D microcontroller with DRV8323 for encoder based PMSM control. I have made my custom code by taking "MonoMtrServo_377s_v1_00_00_00". I am able to run the motor in both direction in FOC and with speed control. But I am about to speed above 1000RPM, the motor makes some weird "tick" noise. The rated speed of motor is 12000RPM.

I am using 6xPWM mode in DRV8323. Since i suspect the PWM configuration, i included PWM config as below.

Switching frequency - 20KHz

void init_pwm(PWMGEN *l_pwm_gen, volatile struct EPWM_REGS * PwmRegs)
{
/* Init Timer-Base Period Register for EPWM1-EPWM3*/

PwmRegs->TBPRD = (l_pwm_gen->PeriodMax/2);

/* Init Timer-Base Phase Register for EPWM1-EPWM3*/
PwmRegs->TBPHS.bit.TBPHS = 0;

PwmRegs->TBCTR = 0;

PwmRegs->TBCTL.bit.CLKDIV = TB_DIV1 ;
PwmRegs->TBCTL.bit.CTRMODE = TB_COUNT_UPDOWN;
PwmRegs->TBCTL.bit.HSPCLKDIV = TB_DIV1;
PwmRegs->TBCTL.bit.PHSEN = TB_DISABLE;
PwmRegs->TBCTL.bit.PRDLD = TB_IMMEDIATE;
PwmRegs->TBCTL.bit.SYNCOSEL = TB_CTR_ZERO;

PwmRegs->CMPA.bit.CMPA = 0;
PwmRegs->CMPCTL.bit.SHDWAMODE = CC_SHADOW;
PwmRegs->CMPCTL.bit.LOADAMODE = CC_CTR_ZERO;

// Action Qualifier SubModule Registers
PwmRegs->AQCTLA.bit.CAU = AQ_CLEAR;
PwmRegs->AQCTLA.bit.CAD = AQ_SET;

/* Init Dead-Band Generator Control Register for EPWM1-EPWM3*/
PwmRegs->DBCTL.all = BLDCPWM_DBCTL_CLEAR_STATE;

/* Init PWM Chopper Control Register for EPWM1-EPWM3*/
PwmRegs->PCCTL.all = BLDCPWM_PCCTL_INIT_STATE;
}

void init_pwm_deadband(PWMGEN *l_pwm_gen, volatile struct EPWM_REGS * PwmRegs)
{
/* Init Dead-Band Generator Control Register for EPWM1-EPWM3*/
PwmRegs->DBCTL.all = BLDCPWM_DBCTL_INIT_STATE;

PwmRegs->DBRED.bit.DBRED = 100;
PwmRegs->DBFED.bit.DBFED = 100;

}

Regards,

kaarthi

over 5 years ago

0 Ramesh Ramamoorthy over 5 years ago

TI__Mastermind 27240 points

I dont think PWM gen is the problem, it may be in your closed loop control or in the motor itself.

0 Kaarthi Chandrasekaran over 5 years ago in reply to Ramesh Ramamoorthy

Prodigy 185 points

Hi Ramesh,

Thankyou for your reply. I tried with open loop control and I tried another motor also, I had same problem.

Note: I tried this complementary pwm mode with dead band in trapezoidal control also, I got the same problem. So I used simple soft switching method as seen in TI's reference design and the problem got solved. That's the reason I suspect PWM config.

Any suggestions would be grateful.

Regards,

Kaarthi

0 Ramesh Ramamoorthy over 5 years ago in reply to Kaarthi Chandrasekaran

TI__Mastermind 27240 points

You are using IMMEDIATE mode update. This will update the compare register at the moment of writing. At higher duty cycles, it will not be ok. Change it to SHADOW mode. This will synchronise all CMP updates corresponding to ZRO or PRD as you select. Pls review the user guide/ TRM for more info. This should fix it.

0 Kaarthi Chandrasekaran over 5 years ago in reply to Ramesh Ramamoorthy

Prodigy 185 points

Hi Ramesh,

I tried with shadow mode setting still I am getting noise and temperature of motor also getting higher. Its going upto 60deg in 1.30hrs at no load. I have attached some waveforms for your reference.

blue - phase current output

yellow - electrical angle

blue - Pwm output of gate driver A-top

yellow - Pwm output of gate driver A-bottom

Dead time - 2us

gate driver - drv8323 evaluation board

Same phase current waveform - sine waveform shape changed at higher speed and also noise becomes higher

0 Ramesh Ramamoorthy over 5 years ago in reply to Kaarthi Chandrasekaran

TI__Mastermind 27240 points

Initially you mentioned about problem with going into higher speed. What was the earlier higher speed you could reach and what is it now?

Secondly, your deadband seem to be much larger for the device, you can reduce it to 0.5 micro second or so. Check the spec for DRV device that you use. This could be leading to higher harmonic current and heating up of motor.

0 Kaarthi Chandrasekaran over 5 years ago in reply to Ramesh Ramamoorthy

Prodigy 185 points

Hi,

Above 1500Rpm I am able to hear the noise clearly.

I have already tested with 400ns deadband, once again I will try with lesser deadband and update to you.

Thanks and regards,

Kaarthi

0 Ramesh Ramamoorthy over 5 years ago in reply to Kaarthi Chandrasekaran

TI__Mastermind 27240 points

Another thing to note - to go to higher speeds, field weakening may be needed for your motor.

0 Kaarthi Chandrasekaran over 5 years ago in reply to Ramesh Ramamoorthy

Prodigy 185 points

Hi,

I tried with 400ns dead time and lesser with 50ns, still the results are same. And about field weakening; I think we need to go for field weakening only when we need to speed above rated speed. But in my case I'm trying only 3000RPM whereas the rated speed of motor is 12000RPM. Correct me if I'm wrong.

Regards,

kaarthi

0 Ramesh Ramamoorthy over 5 years ago in reply to Kaarthi Chandrasekaran

TI__Mastermind 27240 points

Check if the modulation index has maxed out. If you have applied max voltage and the motor speed does not reach 12K rpm, then i would suspect that 12K is the max speed and not rated speed. The speed you get when applying rated voltage is the rated speed.

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