# Motor Control Class: Lecture 6 - Commutation

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## Motor Control Class: Lecture 6 - Commutation

5,885 Views
NXP Employee

In this sixth lecture of the motor control course we discuss about how motor phase commutation works and how can we build a commutation table to ease the software processing to compute the PWM sequence that controls the power inverter which turn the rotor.

Main topics:

- How the rotor turns when voltage is applied;

- How to define the commutation table;

- How to control the power inverter switches;

- How to identify the commutation sequence;

Objectives:

- Understand the concept of 6-step commutation;

- Design the commutation vector table;

- Understand how to operate the power inverter;

- Test your knowledge with a short quiz;

NOTE: Chinese viewers can watch the video on YOUKU using this link

NOTE: Chinese viewers can watch the video on YOUKU using this link

- pdf attached with slides shown in these videos;

3 Replies
4,301 Views
Contributor II

I have tried a few  different orders of Phase A/B/C and Hall 1/2/3. The result communication table had different pattern as yours; is that all right?

If it's true, what's the main reason to cause the pattern difference?

Thanks,

Jd

4,305 Views
NXP Employee

Hi jimduanva‌,

It's true! So this is a very important step in making the BLDC motor working. In fact over last weekend i had to redue the procured for a another motor in order to make it run.

Initially, i thought to save some time and started to play with the CW and CCW tables manually hoping to find a quick setup to work. I managed to spin the motor but very oddly. At some point i've decided to repeat the procedure shown in this lecture and in less than 1h i had the motor running correctly and honestly the commutation tables were totally different than what i was trying to guess.

Here is a good application node that describes in details this procedure.

Hope this helps!

Daniel

4,306 Views
NXP Employee

To test your knowledge or to have a discussion starting point let us have this short quiz session:

Q1: What is the name of the PWM technique used in this lecture to control the power inverter MOSFETs?

Q2: What are the main benefits of this PWM technique?