Why does high-speed rail use AC traction motors in China?
Synchronous excitation motor, more devices, more annoying, generally used in firepower, water power plants. It can be said that the world's larger power motors (1MW or more), basically all communication. The power generation is basically synchronous, and the motor is basically asynchronous. In addition, I give you a data, the world about 70% of the power consumption of the motor, there are 70% of which is asynchronous motor.
The design of asynchronous motor in AC motor is perfect, robust and easy to control. It is absolutely dominant in AC motor. The permanent magnet synchronous machine motor model is also very good, is the main application of high precision digital machine tools, hybrid electric vehicles, but also on some protection measures not in place, there is overheating phenomenon of demagnetization.
I haven't seen anything special about high-speed rail, but it seems that the DC motor doesn't have such good performance. DC brush is very suitable for high power, brush aging is too fast, low efficiency. The essence of DC brushless or AC, is only square wave input, current, power and torque higher harmonic, electromagnetic environment is poor. Moreover, the most widely used brushless DC is still on the computer fan, high-speed rail is not enough power. For the moment, AC motor is the best characteristic. The result of superposition of three-phase sine wave current is a constant constant, without harmonic pollution.
