What is shunting?
As the speed of a locomotive increases, the traction motors generate large amounts of extra electricity that is simply not needed. This creates resistance in the motors (called counter-emf) and reduces the amount of amperage going into the motors, which limits speed. Shunting is a process in which the resistance is reduced by lowering the flow of electricity to the magnets that create the EM field in the motors without reducing the amperage. This lowers the resistance the traction motors face.
