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I have been trying to make a FOC for BLDC motor controlling, but I am stuck at the state that before open loop state which single alignment of the motor control. The question and the explanation is below :

I have applied 24V to the motor from a DC source and made motor's phases A(+) and B(-). I was hoping it should be alignment in same position whenever I apply 24V as it says in the documentation.

Documentation that I have been used:

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The problem is that it is not happening as it should be (like the links above.) It always gets to different position and locks itself (I know because I cannot turn it by hand.) How can solve this issue? I want to obtain same certain position every time like in these documents.

JRE
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Semih Urtekin
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  • What position does it end up in? – Drew Mar 15 '23 at 14:54
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    A real motor doesn't use a pole arrangement like that. Is that what you mean? Real motors have more poles and the energized positions are not mechanically unique. For example, 4 permanent magnet poles and 6 electromagnetic poles. But for commutation you don't need the mechanical shaft position. You just need to know the electrical/magnetic alignment of the poles and phases. – DKNguyen Mar 15 '23 at 15:08
  • related questions: [BLDC motor - initial rotor position](https://electrical.codidact.com/posts/280606) – Nick Alexeev Mar 15 '23 at 15:24

1 Answers1

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I want to obtain same certain position every time like in these documents.

You do, and you don't :)

The position is indeed the same every time, but it's the electrical position. There is usually more than one equivalent electrical position across one revolution. That number of those repeating positions also called the number of electromagnetic or "electrical" poles.

The FOC sees the motor in terms of this electrical position, not the mechanical position, so everything is all right. There's no reason to expect the same mechanical position every time - it's not needed to get the FOC going, as long as the starting electrical position is the same. So far from what you described it works just as it should!

Kuba hasn't forgotten Monica
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  • Thank you all very much for your quick response. What you say is very logical. Since I am still a student and there are not many resources on a complex subject like sensorless FOC, I can sometimes ask such funny questions. Thank you again for enlightening me so much with your answer. I wonder if I have a chance to reach you privately again when I have other questions without disturbing you too much? – Semih Urtekin Mar 16 '23 at 06:26
  • @SemihUrtekin In most cases, that would be called consulting, and that's charged per hour :) Public Q&A is free to you :) – Kuba hasn't forgotten Monica Mar 17 '23 at 14:11