Brushless DC (and variable-frequency-pushed AC) motors are a massive improvement above AC induction motors, since they do away with the need for passing the rotor latest throughout the stator, through the use of a rotating area within the stator to work from the sector of the long lasting magnet rotor, https://damienulhrr.blogoscience.com/35984281/the-smart-trick-of-prescription-sports-glasses-that-no-one-is-discussing