I get to learn about different types of tools and how they work. One of my favorite topics is the difference between brushed and brushless motors. Brushless motors are more efficient, faster and durable than brushed motors, but they also cost more and require more sophisticated electronics. Brush motors are simple, inexpensive, and easy to improve, but they also generate high heat, noise, and wear. I want to compare the pros and cons of both types of motors and see how they perform in different applications. I'm always interested in hearing from other people who share my passion for power tools and motors. If you want to know more about brushless vs brushed motor.

 

Hijacking on AAC is not allowed so now you have a thread of your your of your very own.

This was moved from here:
https://forum.allaboutcircuits.com/threads/brushless-ac-motor-questions.39352/#post-1849322

 

How come the reply was not moved as well?
One of the differences is when used in low RPM situations, BLDC exhibit 'cogging' at low RPM's compared to high pole count DC which have skewed rotor laminations in order to also minimize it.
In precise positioning applications such as CNC and where encoder feedback is used using a PID loop, the BLDC can be made to run as smooth as desired with no cogging effect at all.

 

How come the reply was not moved as well?
One of the differences is when used in low RPM situations, BLDC exhibit 'cogging' at low RPM's compared to high pole count DC which have skewed rotor laminations in order to also minimize it.
In precise positioning applications such as CNC and where encoder feedback is used using a PID loop, the BLDC can be made to run as smooth as desired with no cogging effect at all.

Most of the cheaper BLDC motors are designed (magnet shapes, number of slots, and other geometric features) for 6 step trapezoidal waveform drive so the magnetic flux structure in the motor is optimized for that. PMAC (same electromagnetic theory as a BLDC) motors designed for sinusoidal wave-forms have much less 'cogging' are low RPM. Both generate mainly sinusoidal (the coils magnetic field filters harmonics) back-emf so it's fairly easy to precisely control both with feedback from an encoder at low speeds or BEMF at higher speeds.

https://www.machinedesign.com/motor...-permanent-magnet-and-servomotor-technologies
What's the Difference Between AC Induction, Permanent Magnet, and Servomotor Technologies?

 

The "cogging" is eliminated completely when a PID loop is used as in CNC applications, also I have successfully converted a AC 3ph version to a BLDC application.

 

How come the reply was not moved as well?
One of the differences is when used in low RPM situations, BLDC exhibit 'cogging' at low RPM's compared to high pole count DC which have skewed rotor laminations in order to also minimize it.
In precise positioning applications such as CNC and where encoder feedback is used using a PID loop, the BLDC can be made to run as smooth as desired with no cogging effect at all.

because I wasn't sure whom you were applying to.