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DRV8301-69M-KIT: Cant get sufficient current from motor drive

Part Number: DRV8301-69M-KIT
Other Parts Discussed in Thread: DRV8301

I am using the DRV8301 board connected to a BLDC motor with a maximum current limit of 100 amp. I am running a sample rate of 45 kHz decimated to 15 kHz. It is an 11 pole pair motor and I am driving it using Lab 5b and Lab 10a. I am not using field weakening. The motor has a 258 kv rating and we are using it up to 6000 rpm. The motor was characterized in Lab 2 and has the following setup.

#elif (USER_MOTOR == NeuMotor250V2)
#define USER_MOTOR_Rr (NULL)
#define USER_MOTOR_Rs (0.0146962907)
#define USER_MOTOR_Ls_d (1.03721777e-05)
#define USER_MOTOR_Ls_q (1.03721777e-05)
#define USER_MOTOR_RATED_FLUX (0.00887547713)
#define USER_MOTOR_FLUX_EST_FREQ_Hz (80.0)

Kp_spd = 3.0

Ki_spd = 0.039999

Kp_idq = 0.04336339285

Ki_idq = 0.0944596529

The motor starts and runs well under no load and medium load conditions. I increase the loading until the source motor current (a battery of 28 volts) is approximately 18 amps. It slows a bit from the 6000 rpm but still does well. If I try to increase the load it reaches a point that the motor starts a high pitched squeal and the current will not increase. It seems from what the documents say that it should continue to increase current flow but something seems to be stopping it. The battery is capable of 55 amps continuous (verified) so it does not seem to be the issue. The DRV8301 should run to 60 amps so that does not seem to be the limit. 

Can someone give me a clue where to look to determine the bottleneck please.

  • The maximum peak to peak current of the motor is 82.5A on the DRV8301-kit limit to the current sensing circuit, and it's not equal to the dc input current. The motor phase current is far greater than the dc current. You might use a current probe to check the motor phase current if its peak current is close to the 41.25A. If so, that means the maximum current is limited to the sampling circuit, and the ADC will be overflow.

  • This was very helpful. The current in the motor phase was much greater than I thought and it was doing exactly as designed.