S12ZVM FOC MBD issue

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S12ZVM FOC MBD issue

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Contributor II

Dear Daniel:

I have some questions want to ask you about S12ZVM FOC MBD control. I have run motor successful in EVB use the demo FTF-ACC-F1114_FOC_Sensorless. 

My questions is

1: EVB use the 10mR resistance as the current sensor. and the current scale is 12.5. if I use the 1mR resistance and current scale is 10. how should I modify the parameter in MBD.

2: The demo motor is 4 pole pairs . if the motor is 5 pole pairs. how shoud I modify the parameter in MBD.

thanks very much and look forward to your reply.

Best regards

david meng

1 Reply

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NXP Employee
NXP Employee

Hi dmeng1@stackpole.com‌,

1: EVB use the 10mR resistance as the current sensor. and the current scale is 12.5. if I use the 1mR resistance and current scale is 10. how should I modify the parameter in MBD.

In theory - nothing. The Simulink model uses the int16 fixed point implementation, hence it is not using the actual SI values of the phase currents but rather the PU representation.

The SI unit current is only displayed in the FreeMASTER project. In order to display the current  in AMPS, the transformation is done in FreeMASTER only. That is the place to change based on your new values of the measurement shunt resistors.

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Nonetheless, the maximum current that the drive is capable to read, has another aspects that you need to consider and is not simply obvious -> please refer to the answer of the second question

2: The demo motor is 4 pole pairs . if the motor is 5 pole pairs. how should I modify the parameter in MBD.

thanks very much and look forward to your reply.

The theory of back-EMF estimator and Tracking Observer is discussed here: Module 9: Position Observer (Part 1/2) 

If you change the current scale, voltage, or any of the motor parameters you need to update the Positions Observer gains and constants. In the article pointed above you will find the m-scripts that can help you to compute all the parameters.

Furthermore, you can download one of the latest versions of the AMMCLIB and inside the User Guide Manual you will find more details about the theory of operation of each of the Simulink blocks.

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The pole pairs is not so important for the model, because the model is implemented starting from the assumptions that the entire FOC, Position Observer and Controllers act on the electrical quantities. The transformation between geometric and electrical values are done once again via FreeMASTER. This is where the PP of the motor comes into play.

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Hope this helps!

Daniel