Electric locomotives are a type of traction equipment for rail vehicles, powered by drive motors that rotate the wheels. They utilize the friction between the wheels and the rail surface to move along the tracks. This mode of operation is limited by both the power of the traction motor (or internal combustion engine) and the friction between the wheels and the rail surface. The transport capacity of the locomotive is restricted by the gradient it can handle, with typical track gradients being 3‰, and local gradients not exceeding 30‰. They are categorized structurally into overhead-catenary locomotives and battery-powered locomotives.

Track-mounted electric vehicle

The operation process of overhead line electric locomotives involves high-voltage AC power being stepped down and rectified at the traction converter. The positive pole is connected to the overhead wire, while the negative pole is connected to the rail. The locomotive's collector arm contacts the overhead wire, introducing the current into the train. It then passes through the air automatic switch, controller, and resistor box to the traction motor, driving the motor to operate. The motor, through a drive mechanism, rotates the wheels, thus pulling the train. The current flowing out of the motor returns to the converter via the rail.