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Our Motor was broken by OVER CURRENT while proj_lab10b was running.

ay0689_3
Expert 1085 points

Other Parts Discussed in Thread: DRV8305, CSD, MOTORWARE

Hello, our Motor was broken by OVER CURRENT while proj_lab10b was running.

Totally three Motors were broken by over-current.
Just one coil of U,V,W phase was burnout. But each broken coil was one of U,V,W, randomly.

F28069M device,DRV8305, Shunts and CSD MOSFETs are safe.

Regarding user_j1.h file, our Motor has 3 pole-pairs and the value of Current limit is set by 20.0 A.

<user_j1.h file>

#elif (USER_MOTOR == NEW_MOTOR)
#define USER_MOTOR_TYPE MOTOR_Type_Pm
#define USER_MOTOR_NUM_POLE_PAIRS (3)
:
:
#define USER_MOTOR_MAX_CURRENT (20.0)
#define USER_MOTOR_FLUX_EST_FREQ_Hz (20.0)
#define USER_MOTOR_ENCODER_LINES (1)
#define USER_MOTOR_MAX_SPEED_KRPM (5.0)
:
:

The waveform of Motor current is as follows,

As I set USER_MOTOR_MAX_CURRENT = 20.0, the motor current should be within 20.0A.
But some waveforms were exceeded over 20.0A. 

My MotorWare Version is MW16 and my CCS version is 6.1.2.

Could you please tell me how to resolve the over current problem ?

Best regards,
ay0689

  • 0
    TI__Guru** 117140 points
    USER_MOTOR_MAX_CURRENT is for the maximum torque current (Iq), not the peak current in your waveform, it is far less than the peak current. You need to set the USER_MOTOR_MAX_CURRENT in user.h based on your motor. Please ensure the motor parameters in user.h is correct, and you can use lab02a to identify the motor parameters if you didn't know them.
  • 0 in reply to Yanming Luo
    Expert 1085 points

    Hello, Yanming-san,

    We have already taken the motor parameters many times by using lab02c(FOC) and lab05c(Motion) so far. 

    This was not the motor parameter problem.

    In our motor circuit, a regenerative power consumption circuit was attached,
    but regenerative electric power exceeding that circuit occurred,
    it is thought that overcurrent flowed to the motor, resulting in motor breakage.

    In order to reduce regenerative power, Jerk and motor speed settings of lab10b were changed.
    Jerk did not change much, and changing the speed from 8500 rpm to 7500 rpm, the overcurrent phenomenon disappeared.

    Although the motor speed has decreased, 7500rpm operation is still OK for our application.

    Thanks and best regards,

    ay0689

  • 0 in reply to ay0689_3
    TI__Guru** 117140 points
    Did the motor run in field weakening mode? Regenerative circuit is often used for over voltage protection. It's better to use hardware protection to turn off PWM output to avoid motor over peak current.