BLDC motor coil commutation?

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1

In a 3 phase BLDC motor driver (voltage source inverter)…

If the commutation frequency is 3Hz then it rotates at 1 rev/second.

So the commutation period is 333milliseconds.

However, within the 333 millisecond ON times, the motor coil is PWM’d at high frequency, in order to control the current level.

The point is that sometimes this high frequency PWM’ing is not done…when it is not done, why is it not done?

Why is there literally no article on the internet which explains this?

2

treez:

  1. The point is that sometimes this high frequency PWM’ing is not done…when it is not done, why is it not done?

  2. Why is there literally no article on the internet which explains this?

1) To get full torque.
  1. I dunno.
3

Microchip has a number of App Notes on building/coding BLDC motor controllers/drivers.

Go to their web site and read the App Notes.

4

I think the question about number of poles is a bit more complex since commutation possibly involves a differing numbers of magnets.

http://www.southernsoaringclub.org.za/articles.html – great section on motors

https://www.youtube.com/watch?v=ZAY5JInyHXY - Brushless DC Motors & Control 1

https://www.youtube.com/watch?v=WyQInXjpGwU - Brushless DC Motors & Control 2

also https://www.youtube.com/channel/UC85-Wz … 6qUa6m7DOw may have some answers

-mark