DRV10983: getting stopped in open loop

Hi Art,

Can you please share the motor you are using?

Can you try to disable AVS?

Since this is a ceiling fan application I'm assuming the input voltage is 24V. If this is the case please increase DT to 440ns. 

Are you asking if you can spin the motor at 42 Hz?

Thanks,

Michael

Hello Michael,

The motor is SRM with the below Parameters:

Input Voltage = 24V
No.of Poles = 14
Maximum Speed = 360rpm
Maximum Current = 2A
Phase to Center Tap Resistance = 3.3/2 = 1.65 Ohms
Motor Speed = 360rpm / (60 / 7 pole pairs) = 42Hz
Kt = 24V / 42Hz = 571 mV/Hz

Latest update from the customer:

We have now used the below values for tuning the motor with blade angles of 9.0deg,
R (CP) = 1.7072 Ohms
Kt = 588.8 mV/Hz
Acceleration-1 = 0.28 Hz/s
Acceleration-2 = 0.0026 Hz/s2
Align Time = 0.67 s
Open Loop Current Rate = 6VCC/s
Open Loop/Align Current = 1.6A / 1.2A
Driver Dead Time = 440ns
Disables Closed Loop, IPD, ISD, RD, AVS

When we set the,
Open to Closed Loop Threshold = 25.6 Hz (it is continuously rotating at 200rpm)
Open to Closed Loop Threshold = 38.4 Hz (it is getting stopped at 290rpm)

Thanks and regards,

Art

Hi Art, 

Michael will get back to you shortly on these questions!

Thanks,

Matt

Hi Art,

1. Please see our TI training video on BEMF constant measurements, it will show you how to program that value into the device.  I want you to check this because I want to make sure the programmed Kt is correct.

https://training.ti.com/how-spin-drv10x-family-devices-part-1

2. After programming the measured Kt , enable closed loop in the GUI and set the open loop to closed loop threshold to 25.6 Hz, then try to spin your motor. If a fault triggers please let me know what fault occurred. 

3. If the device triggers an abnormal Kt fault, keep increasing the lead time.  

Regards,

Michael

Thanks Michael. I'll inform customer.

Best regards,

Art

Art,

Sounds good, let me know if they have any further questions.

Regards,

Michael

Hi Art,

Was the customer able to resolve their issue? Is there any other assistance I can provide?

Regards,

Michael

Hello Michael,

Customer have not send their feedback yet. I think its okay to close for now. I'll just reach-out in case they reply back.

Thanks and regards,

Art

Hello Michael,

Customer just sent a reply now. Blow is their response in verbatim:

"I don't think it's possible to get the BEMF in magnet-less motor? We are working on brush-less DC motor based on switched reluctance concept - SRM.

They are trying to get some waveforms using oscillospcope, but the waveforms are not getting generated.

Thanks and regards,

Art

Hello Michael,

Customer is grateful for the information but is asking how come its rotating at the 330rpm?

Thanks and regards,

Art

Hey Art,

The srm works based on reluctance torque, so when the stator coils are excited there will be some reluctance torque generated which can spin a motor. Ideally we don't recommend to use this device to spin a srm, it's designed to spin a BLDC motor.

Thanks,

Michael

Hi Art,

Does the customer need any additional help on this, or am I OK to close this thread?

Regards,

Michael

Hello Michael,

Customer no longer have further inquiries. It's okay to close now. I'll just inform you in case they have follow up questions.

Thanks and regards,

Art