MCT8315EVM: Unusual behaviour of the rising floating phase

Hi Marco,

I will need some time to look into this, I will aim to get back to you by next Thursday.

Regards,

Joshua

Hi Joshua, 

Did you find out anything?

Regards
Marco

Hi Marco,

If the zoomed in portion of the capture that you provided is occurring while the algorithm state is in open loop then the device does not know the true BEMF zero crossing leading to asymmetrical phase voltages since the device does a "blind commutation" while in the open loop state.

If this is occurring while the device is occurring while the algorithm state is in closed loop then adjusting the blanking time [TBLANK] would help to get all three phase voltages symmetrical.

Regards,

Joshua 

Hi Joshua, 

In my opinion, "open loop" during the startup phase means that the commutation time is permanently reduced with each commutation without looking at the BEMF (determined by startup ramp parameters A1 and A2) and only in the "closed loop" is the zero crossing used as reference.
Or what is this startup algorithm looking at if it still has to regulate the commutation time?

My original question was:
What is the advantage of the extended commutation period and how is it determined?

Thank you for your time.

Best regards, 
Marco

Hi Marco,

I will sometime to look further into your question. I will aim to get back to you by Dec. 1.

Regards,

Joshua

Hi Joshua, 

Did you find out anything?

Regards
Marco