What is the power source and running principle of the train?

Electric locomotives and internal diesel locomotives are traction motors; Internal combustion-diesel hydraulic pressure is the power transmitted by diesel engine through working oil; There are also some heavy rail vehicles with mechanical transmission, which use mechanical gearboxes and gears to directly transfer the power of diesel engines to the moving wheels of automobiles. Among the vehicles, the vehicle in the middle part of the green leather car is equipped with a generator, and the vehicle is driven by the wheelset when driving; Red leather cars and blue leather cars (25K, 25G, 25T series) are not equipped with generators to generate enough electricity because of the large electricity consumption of air conditioning devices. Some of them rely on KD (air-conditioned generator car with diesel generator set inside) to generate electricity and supply power to vehicles; There is also a part (mainly a part of 25k and 25t models) that directly supplies power to vehicles by locomotives equipped with train power supply devices (diesel locomotives are DF4DF, DF 1 1G, electric locomotives are SS8 locomotives, SS9G locomotives, etc.). ).