AMF-IND-T3033 - 2018 Kinetis Motor Suite Hands On Training_final.pdf

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AMF-IND-T3033 - 2018 Kinetis Motor Suite Hands On Training_final.pdf

AMF-IND-T3033 - 2018 Kinetis Motor Suite Hands On Training_final.pdf

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Hallo Philip,

really interesting doc.

Just a question: at pag 52 of the doc you wrote: 

3-phase back EMF voltage

as an ADC features for FRDM-LVPMSM card. But if you take a look at the electric diagram you see that there are only the Current feedbacks, no feedback for the Back-EMF.

FRDM-LVPMSM Electric Diagram -- Pag5.jpg

Is there some mistakes in the electric diagram? Or maybe you mean Back-EMF feedback as a Leg Current Feedback.

This topic is important for me because in the HVP-MC3 board there is written that there is either the LEG CURRENT FEEDBACK either the BACK-EMF feedback.

So, for the right working of the FOC is it necessary to have the feedback also of the BACK-EMF?

HVP-MC3 Electric Diagram pag8.jpg

Thanks for explaining

Best Regards


my understanding is that the feedback for the control loop is commonly referred to as Back EMF.  

The back EMF signal in an FOC loop is the current converted to voltage in the phases of the motor.  

The back EMF signal in a sensorless BLDC is a voltage input to the control loop, not a current.  

This difference is effected in the actual hardware, where a PMSM loop measure the current in the motor phase by adding a shunt resistor and the back EMF voltage is measured in a non-active phase of the motor winding. The HVP platform can work with either the bldc sensorless or FOC modes depending on the choice of feedback input you choose.  

I hope this helps.


Hallo Philip,

sorry for this dealy in reply to your comments, and, of course, thank you very much for explaining.

I would only underline that the BACK EMF is a FEEDBACK generated by the motor itself, and could be very difficult to measure at a very low RPM, since the EMF generated is proportional to the speed of the motor and, furthermore, says nothing regarding the TORQUE generated at a fixed speed, you have to read also the current per phase.

I have some doubt regarding the KMS Software: is it possible also to test a trapezoidal zero-crossing software control? If I understood correctly, I can only implement FOC driving method. This is the reason why I am wondering why there is also the Back-EMF feedback, since these signals are not used in the FOC tecnique (or do I miss something of that software)?

Thank you again for answering me!

Best Regards


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