| The EMU study conducted early aboard, many countries have mature EMU technology, particularly Japan, France and Germany. China's railways increased a large number of high-speed EMU during the Sixth Speed. To carry out the speed, China's experts localization CRH 2 high-speed train,which the Ministry of Railways introduce to Japan by Kawasaki Heavy Industries.Braking is the protection of the safe operation of the train, braking technology is an important part of train technology. Brake manner of EMU, according to the method of braking force generated can be divided into friction braking, dynamic braking and magnetic braking.According to the manipulation, it can be divided into air-brake, air-electrical brake and electrical power brake. CRH 2 EMU used type of air brake and regenerative braking combined braking mode, with its excellent braking performance to ensure the safe operation of the train.CRH 2 type Braking system consists of electric braking system, air brake system, anti-skid brake device and control system components, with brake, rapid braking, emergency brake, auxiliary brake system and resistance to snow brake, etc. EMU braking controled by the BCU (Brake control unit). BCU method using micro-processing digital computing. BCU calculate the regenerative braking force and the braking force to the air distribution, according to the load compartment to the signal and speed of information needed for braking.Train deceleration force composed by brake force provided by of their own power and the resistance component of it when the train runs. Train braking force no larger than adhesion between wheel and rail, or will the wheel "locking" to pose a threat to the safety of passengers. Adhesion on the train, deceleration forces, braking time and braking distance is calculated in the paper. Then deceleration and speed curves, electric air distribution curves during the train braking were obtained. And wheel wear under EMU braking performance was also calculated, which verifies the CRH2 EMU type braking system can meet the security requirements.CRH 2 EMU's electric type brake is regenerative braking, and the control of traction converter for the process in the regenerative braking is essential. Traction converter is composed by a single-phase three-level pulse rectifier, DC intermediate link and the three-phase three-level inverter. During traction process,1500V AC come from the transformer through a pulse rectifier changed into 2600V～3000V DC, then comes into a three-level inverter with adjustable voltage and frequency AC for traction motor. Regenerative braking process is the anti-traction process, the kinetic energy was changed into electricity back to electronic network. The process of regenerative braking pulse rectifier is simulated on the paper, obtained voltage waveform during regenerative braking. In which the method of single-phase three-level PWM rectifier is the transient direct current control, using SPWM modulation, three-phase three-level inverter control method if the vector control using SVPWM modulation. |
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