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DRV8301-69M-KIT: Not spinning above a certain RPM

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

Hi there

We have designed our own surface mounted PMSM motor, and trying to drive it with the DRV8301-69M-KIT. We have followed the PM sensorless field orientated control module supplied with the kit, with everything working correctly up to level 7. 

However when we try to spin the motor above 900 RPM, the board shows a fault, with the fault LED being turned on. We have looked at DRV8301_stat_reg1 and it shows that:

DRV8301_stat_reg1.bit.FETLA_OC = 1

namely that the C phase on the low side FET is being called to high. This testing is being put under no load with the motor being designed to spin at 1500 RPM. The current levels at this point is at 2.1A, but when the rpm is set higher, a large current spike is drawn and the board shows a fault. This seems to be an issue with the board itself, as the motor is well within the parameters given.

Any help would be greatly appreciated.

  • What example lab or project are you using? And can you share some of the measurement motor phase current waveform to show the issue you mentioned above?

  • We are using the project called PM_sensorless from \development_kits\DRV830x-HC-C2-KIT_v105\PM_Sensorless.

    We can't currently show the phase current waveform, but will be able to send it within the next few days. However it seems that when we set the reference speed of the motor to 60Hz, with the pole count being 8, that the base speed should be 900 RPM. 

    We run Level 7 Incremental Build of the project and find that from switching lsw=1 to lsw=2, that a drop in speed is found under no load. When we try to bring the motor up to 1.0pu to reference speed, and further set the Iq_ref to 0.2, that the motor operates for around 3-4 seconds before the fault LED turns on and the field of the stator is not present, causing the rotor to come to a halt. We are not able to identify why the fault occurs, as we are below the current draw of the FETS.

    Is it possible that the SMO version and speed_est.h file we are using is to old and that we require to use a more later version?

  • Please make sure that you set the right motor parameters like Rs, Ls for SMO. Can the motor run up to the speed you want if there is no any load on the motor?

    There is no any update in controlSUITE for a few years. You may try to implement the examples in the Motor Control SDK if you want to use the latest C2000 device.

  • Good day 

    We will look at adjusting the motor parameters properly. However, these speeds all operate under no load condition.

  • Oj. As mentioned above, the right motor parameters are very critical for the sensorless-FOC with SMO/eSMO. You may check if the estimated rotor angle is correct as shown in the example project if the motor has a position sensor.

  • Good day

    We adjusted the motor parameters much more and we further tuned the SMO, with the system not responding as well as well as we hoped. We then added an encoder onto the system and set the feedback of the encoder to the Speed PID loop. This also did not seem to help. I have attached a few images to show the waveforms of the current and voltage:

    The Blue waveform is the phase voltage of the motor (Phase A), the red is the DC current into the control board and the green waveform is the DC voltage into the control board. This is occurring at steady state at 750RPM. It is observed that the current being drawn is around 800mA.

    However when the the controller is asked to increase the speed to 825 RPM, the current starts to oscillate and waver. Attached is where a major error occurs

    It can be seen that the DC current in oscillates majorly, and actually becomes negative when the motor speed is increased for a short time. This causes the phase voltage to have oscillations at the peaks as seen below

    Another instance of operation is where we are measuring the phase current and the short circuit appears. 

    We think the issue may be on the DRV chip that the VGS is to low or climbs to slowly and may cause the VDS to shoot up and cause the latch down of the MOSFET by the DRV chip. Would this be a cause?

  • Did you capture any motor phase current waveform to show this usse? And did you try to run the motor in the build level 3&4 to verify the current sensing and speed measurement/estimation?