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Motor Stall during Torque Current Test

James McKenna
Prodigy 136 points
Part Number: TMS320F28069M
Other Parts Discussed in Thread: DRV8353

Hey yall,

I'm having trouble with a DRV8353/ F28069M custom board with a modified Lab05a to work with our hardware. In our experiment we have a VFD putting a constant forward load on our motor. We apply negative torque to brake and that current recharges a battery. Here are some of our user.h parameters:

USER_IQ_FULL_SCALE_FREQ_Hz             (678.0)
USER_IQ_FULL_SCALE_VOLTAGE_V         (200.0)
USER_ADC_FULL_SCALE_VOLTAGE_V     (66.08745)
USER_IQ_FULL_SCALE_CURRENT_A       (127.0)
USER_ADC_FULL_SCALE_CURRENT_A   (165.0)
USER_MOTOR_MAX_CURRENT                   (120.0)

When IqRef_A is set to a value above 43.0 A the motor starts making a grinding sound and we lose control over our software, we can see the current waveform on a phase wire is going wild. No faults in EST or CRTL but once we tripped an OCP fault from the SPI.

40A is around -6.0 Nm of torque. Our target is about -9.0 Nm for our application. Bus voltage should never go above 60 V.

My suspicion is that this is a IQ value being oversaturated somewhere, that might explain the software going haywire.

Any suggestions would be much appreciated.

  • 0
    TI__Guru** 116570 points

    1. Do you run the lab02b to identify the motor parameters with your own board?

    2. Any load is adding on the motor when you start to run the motor with lab05a?

    Having an incorrect Rs value (especially a value higher than the actual Rs) will make the start-up behave poorly. You might refer to chapter 14 "Managing Full Load at Startup, Low-Speed and Speed Reversal" in InstaSPIN-FOC and InstaSPIN-MOTION User's Guide

    https://www.ti.com/lit/spruhj1

    1. Enable stator Rs recalibration before startup
    2. Enable forced angle
    3. Make sure that the current ADC offset is calibrated.
  • 0 in reply to Yanming Luo
    Prodigy 136 points

    This is very insightful thank you.

    1. We re-identified the motor parameters and they are the unchanged from what we use in our experiment, nothing seems unusual to me.

    USER_MOTOR_Rs                         (0.0428303704)
    USER_MOTOR_Ls_d                     (0.000183131488)
    USER_MOTOR_Ls_q                     (0.000183131488)
    USER_MOTOR_RATED_FLUX    (0.0802721009)

    Current offsets (0.6688213348), (0.6689323783), (0.6507359147)
    Voltage offsets (0.1334835291), (0.1330400109), (0.1324932575)

    2. We initially start our motor with no load. Rs recalibration, current/voltage offsets, and forced angle flags are all enabled. After run_identify is complete we set the VFD to 20 Hz forward direction. The load current exceeds what our motor can overcome in the reverse direction so we may observe the torque output.

    Any other potential problems? For now I will read through this chapter to see if there are any hints to solve this.

  • 0 in reply to James McKenna
    TI__Guru** 116570 points

    Any happens if you use the lab05b to start and run the motor? 

    James McKenna said:
    USER_IQ_FULL_SCALE_VOLTAGE_V         (200.0)
    USER_ADC_FULL_SCALE_VOLTAGE_V     (66.08745)

    You may set USER_IQ_FULL_SCALE_VOLTAGE_V  to a lower value close to USER_ADC_FULL_SCALE_VOLTAGE_V.

  • 0 in reply to Yanming Luo
    Prodigy 136 points

    The lowest setting we can have for USER_IQ_FULL_SCALE_VOLTAGE_V  is 103.0 V to satisfy the constraint USER_IQ_FULL_SCALE_VOLTAGE_V > 0.5 * USER_MOTOR_MAX_CURRENT * USER_MOTOR_Ls_d * USER_VOLTAGE_FILTER_POLE_rps

    where USER_VOLTAGE_FILTER_POLE_rps is (9,314.67380)

    I will set up Lab05b and see if I can get the motor to function.

  • 0 in reply to James McKenna
    TI__Guru** 116570 points

    What's the PWM frequency you using? Why do you use so high USER_VOLTAGE_FILTER_POLE_Hz? Seems like the motor you used is not a high speed motor, you should change the analog voltage filter with 300~800Hz pole frequency.

  • 0 in reply to Yanming Luo
    Prodigy 136 points

    Our PWM frequency is 20kHz. We have a 10 pole pair motor with a target RPM of 3000. We will try setting the filter pole frequency hardware to 500Hz at a minimum and update the software setting.

  • 0 in reply to James McKenna
    TI__Guru** 116570 points

    OK. You may tune the gains of PI controller and set a right reference torque current to start the motor if you want to use the lab05a. It's better to add a ramp control for setting the reference torque current.