What is the primary advantage of using AC traction motors over DC traction motors in modern locomotives?

The primary advantage of using AC (Alternating Current) traction motors over DC (Direct Current) traction motors in modern locomotives is their significantly improved reliability and reduced maintenance requirements due to the absence of commutators and brushes. DC traction motors use a commutator, a rotating mechanical switch, and brushes, which are stationary carbon contacts, to transfer electrical current to the rotating armature windings. These components are subject to wear and tear from friction and electrical arcing, requiring fr....