In the BLDC motor block, a non-standard d'q' Transformation is used. Does this affect the values of L_d and L_q?

Hi all,

I am looking to simulate a BDLC motor using the BLDC block included in the Motor Control Blockset.

As is described in the documentation for the block (https://www.mathworks.com/help/mcb/ref/bldc.html), a different d'q'-Transformation is used to model the BLDC instead of the standard dq-Transformation. Most importantly for my issue, the voltage is calculated by

instead of how it is calculated during standard dq-Transformation:

.

I am curious about the additional scaling factor of π. Why is it used during transformation?

Also, is the value of affected by this? More specifically, if i know the value of and in standard dq-coordinates, can i input these directly into the BLDC motor block or do i need to account for the different d'q'-coordinates first?

Best Regards

Answer 1

[Shivam Gothi]

Hello @Oskar,

I understand that the factor of “pi” is not as per the intended equation. To investigate, I analysed the subsystem blocks found inside the “BLDC” by selecting the block and then pressing “Ctrl+U”. To the best of my knowledge, I found that the equations coded inside the Simulink block are:

Upon reviewing, the factor of “pi” is indeed not included in the actual implementation, and it seems to be a typing mistake in the documentation. I also tried to run the BLDC control example and found it to be working satisfactorily.

Therefore, the equations are correctly implemented as pointed out by you. The factor of “pi” is a documentation error.

I hope this clarifies the situation !

[Oskar]

Hi @Shivam Gothi,

thanks a lot for your response.

I also checked the BLDC block and think the factor of π is wrong in the documentation. I have contacted the MathWorks Support Team about this issue. I guess their response will provide a final answer.

Regards

Answer 2

[MathWorks Motor Control Blockset Team]

Thank you for providing your valuable feedback. The factor of π is a typographical error in the documentation and will be corrected in a future release. Here, d-q and d'-q' are in the same rotor position reference frame, hence Ld and Lq will not be affected.