MCT8329EVM: Current Limit

Hi Prabhat, 

Can you provide the Align Current limit you are targeting, the max peak current of your motor, and the values selected for CSA_GAIN, RSHUNT, and VREF_SEL?

Regards,

Joshua

I am aiming for a 3A current limit for aligning, CSA_GAIN is set at 40V/V, VREF_SEL = UNI DIRECTIONAL, Rsense=0.001

Peak current of motor is 35A for 30 sec

Hi Prabhat, 

From the settings you provided I get that you should set the Align Current limit to 0.2V, which sets the align current to 3.125A. I would also recommend setting LOCK_ILIMIT to 1.2V (28.125A) or 1.3V (30.625) and keeping every other current limit setting below the LOCK_LIMIT setting to help protect your system. 

Did the motor move or was there any noise coming from the motor before the motors burned? 

Regards,

Joshua

Yes there was a noise.

Also an oscillating behavior going back and forth

One more thing what should I do if motor fails to start and triggers loss of sync when I keep the align current limit at 3 amps??  Asking this because this has happened

Hi Prabhat,

PRABHAT RANJAN TRIPATHI said:

One more thing what should I do if motor fails to start and triggers loss of sync when I keep the align current limit at 3 amps??

To fix the motor stalling I recommend trying the following changes:

1. Increase the align time to 2 seconds
2. Change the align ramp rate to 0.2V/s
3. With the align changes the motor should remain still for a small amount of time before going into open loop. If the motor is oscillating when going into open loop, try decreasing the Align Current limit
4. Decrease the open and closed loop acceleration rates to 20Hz/s
5. If the motor still stalls after lowering the acceleration rates, try and increase the CBC_ILIMIT value and OL_ILIMIT value if the motor is stalling during open loop. Do not increase either OL_ILIMIT or CBC_ILIMIT beyond the LOCK_ILIMIT value.

If the motor fails to start spinning or stops spinning. Stop the motor as soon as possible to prevent damage to the motor.

Regards,

Joshua