BLDC/PMSM parametrization based on datasheet

Hello everyone,

I would like to ask regarding parameterization of BLDC/PMSM based on manufacturer's datasheet. I have a motor datasheet in which interphase-resistance, induction values and number of poles are given? The datasheet is hereby attached. The circled part is my requirement for motor. Could you please guide how to do I calculate:

1. D&Q Inductance
2. Torque/BEMF constant or permanent flux linkage
3. Phase resistance

I believe many manufacturer do not simply provide constant values. Looking forward to hearing from the expert in this field.

Thank you.

Answer 1

[Joel Van Sickel]

Here is a good starting reference for the first question: https://www.mathworks.com/matlabcentral/answers/2092156-how-to-calculate-max-permanent-flux-linkage-and-rotor-angle-over-which-back-emf-is-constant-for-a-bl

what block are you using? In general, it would be better to specify your phase inductance and let the block handle the d/q transformation as technically the answer is different based on your reference frame. Now, for the given motor, Ld and Lq could be identical, in which case the reference frame doesn't matter for specifying (highly likely in your case). However, if they don't give you the Ld and Lq values, it's hard to extract them just from a single inductance value. Technically, a better approximaiton is:

• Ld = Ls + Ms + 3/2 Lm. Ld is the stator d-axis inductance.
• Lq = Ls + Ms − 3/2 Lm. Lq is the stator q-axis inductance.
• L0 = Ls – 2Ms. L0 is the stator zero-sequence inductance.

but you need to know your mutual inductance Ms and stator inductance fluctuation Lm (assume 0 if you don't know).

Your phase resistance is likely the interphase resistance listed. It is good to make sure you know wether you are using a wye or delta wound motor.

The unfortunate reality is that most data sheets don't contain enough data to have an accurate dynamic simulaiton of a motor. You can usually guestimate something close enough that has reasonable power current and voltage levels, but it won't quite be right. To really get the data, the vendor either has to give it to you, or you have to extract that data through lab testing once the motor has arrived. The motor control blockset actually has algorithms that you can use to automatically extract these values if connected to an inverter and sensors to drive the motor with. https://www.mathworks.com/help/mcb/gs/estimate-motor-parameters.html

[Hassan Ali]

Thank you! Surely I will look into it.