Research On The Electromagnetic Emission Characteristics Of High-speed Maglev System

The high-speed maglev system adopts the long-stator linear synchronous motor,which can be driven by the guide rail.The maximum speed of the train can reach 600km/h.However,the electromagnetic emission from the high-speed maglev system may affect the passengers and some small equipment in the carriage.Because the radiation frequency,distribution and structure of the main electromagnetic emission sources of high-speed maglev are far different from that of traditional high-speed EMU trains,this thesis presents a new research method for analyzing electromagnetic emission characteristics of high-speed maglev system.This thesis firstly introduces the high-speed maglev power supply system and discusses the potential source of electromagnetic emission of high-speed maglev.Among them,the long-stator linear synchronous motor is the biggest electromagnetic emission source of high-speed maglev.By adjusting the air-gap magnetic field,the train can be suspended and driven at the same time,but the magnetic field will produce leakage from both sides of the tangential section of the motor.Therefore,the air-gap magnetic field,the source of electromagnetic emission of linear motor,is studied in this thesis.By establishing a two-dimensional finite element model of linear motor and verifying it with mathematical method,the different factors affecting the air-gap magnetic field of linear motor are studied.The influence of air-gap magnetic field changes was analyzed by calculating the force of linear motor through virtual force method.Through the study of this part,the electrical parameters are found when the linear motor produces the maximum electromagnetic emission under the actual operation of high-speed maglev train.Then,the current source of low-frequency ac emission of linear motor,that is,high-speed maglev current conversion system,is studied.The conversion system and control module are designed and simulated in Simplorer,and the performance of different conversion units is discussed.The output voltage and current waveform of the conversion system are discussed and analyzed through the joint simulation with the linear motor model.Through the joint simulation of the circuit model and the linear motor model,the output voltage and current waveform of the conversion system is studied,and the influence of the fundamental frequency and the high-order harmonic component of the armature current of the high-speed maglev linear motor on the translation speed of the rotor and the modulated carrier is discussed through the spectrum analysis.Finally,the three-dimensional finite element simulation model of linear motor was established in Maxwell 3D Finally,Maxwell 3D was used to build a three-dimensional finite element calculation model of linear motor.Combined with the high-speed maglev vehicle model,the electromagnetic emission characteristics of linear motor of high-speed maglev train were studied with special consideration for the train running speed.By sampling the calculated results and comparing them with the relative magnetic field emission limits,the maximum magnetic field emission at each sampling point in the carriage is analyzed.The results show that the main distribution frequency and magnitude of low-frequency ac magnetic field emission will change with the change of train speed.In addition,this thesis also analyzes the influence of armature three-phase ac current balance on low-frequency magnetic field emission characteristics through fault state simulation.The distribution of low-frequency magnetic field emission of high-speed maglev linear motor under normal working condition and abnormal working condition of motor lacking phase on one side was compared.The results show that the low-frequency electromagnetic emission of linear motor meets the requirement of corresponding limit when the armature current is balanced.However,under the condition of one-side motor lacking phase,the magnetic field in the carriage is generally shifted to the side of the motor lacking phase,and the amplitude is increased by nearly 10 times,which causes an adverse effect on passengers wearing cardiac pacemakers and cochlear implants.Therefore,it is adviced that the balance of three-phase armature current should be detected and regulated in real time during the actual running of the train to prevent the increase of low-frequency electromagnetic emission in the carriage.By adding a thin layer of 1.5mm silicon steel to the floor,the magnetic field emission in the vehicle under this working condition can be effectively suppressed,and the corresponding limits can be met.