Electric locomotives are a type of traction equipment for rail vehicle transportation, powered by drive motors that rotate the wheels. They rely on 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 gradient capability of locomotive transport is restricted, with the general gradient of the transport track being 3‰, and the local gradient not exceeding 30‰. They are categorized structurally into overhead-wire locomotives and battery-powered locomotives.

Overhead trolley motor

The operation process of overhead trolley cars involves high-voltage AC power being stepped down and rectified at the traction converter. The positive terminal is connected to the overhead wire, while the negative terminal is connected to the rail. The trolley's collecting arm makes contact with the overhead wire, introducing the current into the carriage. It then passes through an air-operated switch, a controller, and a resistor box before entering the traction motor, driving the motor to run. The motor, through a transmission device, rotates the wheels, thereby pulling the train. The current exiting the motor returns to the converter via the rail.