Electric locomotives are traction devices for rail vehicle transportation, powered by drive motors that rotate the wheels. Through the friction between the wheels and the rail surface, the locomotive moves 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. The locomotive's ability to climb gradients is restricted; generally, the gradient of the transport track is 3‰, and the local gradient cannot exceed 30‰. They are categorized structurally into overhead-line locomotives and battery-powered locomotives.

Overhead Trolley Motor Car

The working process of overhead line electric locomotives involves high-voltage AC power being stepped down and rectified by 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 an air automatic switch, controller, and resistor box to the traction motor, driving the motor to operate. The motor, via a transmission device, rotates the wheels, thus propelling the train forward. The current flowing out of the motor returns to the converter via the rail.

Battery-powered electric trolley