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DRV10975: About No motor fault of DRV10975

Chris Jiang
Prodigy 120 points
Part Number: DRV10975

Hello BLDC team:

I have some questions about "No motor fault" of DRV10975，Pealse help me to confirm.

When I config the "no motor fault" enable ,the motor will startup fail at  sometimes(the motor in the hot condition,Ambient temperature is about 60°C) .And when I config the "no motor fault" disable,the motor can startup at all the time.All config and condition environments are the same,except the config of "No motor fault”.

About no motor fault description in the SEPC is like this:The phase U current is checked after transitioning from open loop to closed loop. If phase U current is not greater than 140 mA then the no motor fault is treated and reported as a fault.

So ,my question is:

1.Is the no motor detect  always available? Including  open loop、the moment of  transitioning from open loop to closed loop、 the closed loop?

2.140mA is RMS or the peak value of phase U? I reduce the speed of  the motor in closed loop and abserve the current of phae U with oscilloscope,when the vaule(Rms and max) are less than 140mA,there is no fault reported ,and motor can work normally.Also I config the "no motor fault" enable.

3.Lock detect schemes like the following picture,No motor fault  use the dotted line,is different from the others? 

Looking forward to your reply.

Best Regards!

Chris

  • 0
    TI__Mastermind 18916 points

    Hi Chris, 

    Some of our team members are currently out on business travel, but we will try to get you a response by end of week 

    Best Regards, 
    Andrew 

  • 0
    Prodigy 120 points

    Hello Andrew:

    Thanks for your quickly response.

    The matter is a little urgent. Please give priority to it.Our production line is waiting for confirmation.

     

    Best Regards!

    Chris

  • 0 in reply to Chris Jiang
    TI__Mastermind 18916 points

    Hi Chris, 

    Understood and we will try our best to give you a timely answer 

    In the meantime, just wanted to ask a few questions to see if we can narrow down the issue: 

    1. so for the motor start-up sequence, is there a way to check if the same 'No Motor Fault' trigger occurs from motor starting up in a slightly colder environment? (e.g. 25C ambient temp) 
    2. how immediate is the fault occurring after start-up? does the motor driver system at least attempt some activity?
    3. is the motor driver system starting up from a completely resting/idle state? or did it recently shutdown & restart? 

    Best Regards, 
    Andrew

  • 0 in reply to Andrew Liu
    Prodigy 120 points

    Hello Andrew:

    Following is my replay for you quesiton:

    1.At 25°C ambient temp can successfully start-up all the time and no fault is treated;

    2.I abserved the current of phae U with oscilloscope,likely the moment transitioning from open loop to closed loop.Because of the motor is in the closed cavity,I can't see the motor.The next step I will move the motor out of the cloesd cavity .

    3.Yes ,the motor start-up at completely static state.

    I do the test like this:

    a.start-up the motor at about 25C ambient temp(can start-up all the time),aging 15mins;

    b.Shut down the power  1mins

    c.Restart the motor(this conditon closed cavity temp is about 60C),sometimes can't start-up and "no motor fault" is repoated,when I disable the lock detection the motor can successfully start-up all the time. 

    Best Regards!

    Chris

  • 0 in reply to Andrew Liu
    Prodigy 120 points

    Hello Andrew:

    Following is my replay for you quesiton:

    1.At 25°C ambient temp can successfully start-up all the time and no fault is treated;

    2.I abserved the current of phae U with oscilloscope,likely the moment transitioning from open loop to closed loop.Because of the motor is in the closed cavity,I can't see the motor.The next step I will move the motor out of the cloesd cavity .

    3.Yes ,the motor start-up at completely static state.

    I do the test like this:

    a.start-up the motor at about 25C ambient temp(can start-up all the time),aging 15mins;

    b.Shut down the power  1mins

    c.Restart the motor(this conditon closed cavity temp is about 60C),sometimes can't start-up and "no motor fault" is repoated,when I disable the lock detection the motor can successfully start-up all the time.

    I  added some content that I tested today.I tested the current of phase U,Fowllowing is the picture of deferent start-up config and temp

  • 0 in reply to Chris Jiang
    TI__Mastermind 18916 points

    Hi Chris, 

    Thanks very much for the waveforms - I believe this will be helpful in the debug 

    If possible, please give our team until the end of the week to look into this issue further. 

    Best Regards, 
    Andrew 

  • 0
    TI__Mastermind 24405 points

    Hi Chris,

    Here's my response.

    Chris Jiang said:
    1.Is the no motor detect  always available? Including  open loop、the moment of  transitioning from open loop to closed loop、 the closed loop?

    No motor fault is available only during open loop. This is checked during the open to closed loop transition. if the current during this period is less than 140 mA, device triggers no-motor fault. This fault does not get triggered in closed loo;. For example, if the closed loop current is less than 140 mA, this fault will not get triggered.

    Chris Jiang said:
    2.140mA is RMS or the peak value of phase U? I reduce the speed of  the motor in closed loop and abserve the current of phae U with oscilloscope,when the vaule(Rms and max) are less than 140mA,there is no fault reported ,and motor can work normally.Also I config the "no motor fault" enable.

    140 mA is peak value. 

    Chris Jiang said:
    3.Lock detect schemes like the following picture,No motor fault  use the dotted line,is different from the others? 

    I think the dotted lines indicate that this fault is active only during open loop and not during the entire motor operation.

    Regards,

    Vishnu

  • 0 in reply to Vishnu Balaraj
    Prodigy 120 points

    Hello Vishnu:

    Thanks for  response.

    I have further questions, please help to confirm.

    Above are the waveforms of motor starting under three different conditions.The start-up OK and start-up fail waveforms look like the current amplitude of U phase is the same.The "Open loop/Align current" config is :0.2A/0.15A.I also compared their timing and found that the current of U-phase became zero during the transition from Open loop to Closed loop when the motor start-up fail.Is the No motor fault detected first and then the drive is turned off, or is the current zero due to other reasons? I can't see the logical relationship from the waveform,Please help to check.

    25°C the motor Rph-ct=5.7Ω，and 60°C the motor Rph-ct=10Ω. So，Could it be that the current is not enough for 140mA due to the increase of coil impedance?

    Startup OK VS Start NG Sequence：

    Best Regards!

    Chris

  • 0 in reply to Chris Jiang
    TI__Mastermind 24405 points

    Chris,

    No motor fault gets triggered only at the end of open loop operation. Do you have No motor fault enabled in NG?

    Regards,

    Vishnu