advantage:
a) The speed change is stable and almost no vibration is felt;
b) Low temperature rise and good reliability;
c) The price is low, so it is selected by many manufacturers.
Disadvantages:
a) The carbon brush is easy to wear, which is troublesome to replace and has a short service life;
b) The operating current is large, and the motor magnetic steel is easy to demagnetize, which reduces the service life of the motor.