Disadvantages of brushed motors: 1. The sparks generated by mechanical commutation cause friction between the commutator and the brush, electromagnetic interference, high noise, and short life. 2. Poor reliability and many failures, requiring frequent maintenance. 3. Due to the existence of the commutator, the inertia of the rotor is limited, the maximum speed is limited, and the dynamic performance is affected. Since it has so many shortcomings, why is it still widely used, because it has high torque, simple structure, easy maintenance (ie, carbon brush replacement), and cheap. DC motor – brushless motor Brushless motor is also called DC variable frequency motor (BLDC) in some fields, it uses electronic commutation (Hall sensor), the coil (armature) does not move the magnetic pole, at this time the permanent magnet can be online The outside of the coil can also be inside the coil, so there is a distinction between an outer rotor brushless motor and an inner rotor brushless motor.