Studies On Control Technology Of Brushless DC Motor In Railway Switch

The dissertation proposes control technology of rare earth permanent magnet brushless DC motor (BLDCM) in railway switch. Railway switch is one of important railway electrical signal devices. Generally, it is used to change the switch of railway tracks at cross ways and indicate the switch's position.First, the dissertation summarizes the properties, developing state and application fields of BLDCM, then its fundmental structure; operation principle and control strategy is also presented. On the base of roundly analyzing all kinds of the drive motor in electromotion type railway switch, BLDCM is proposed to replace the formerly traditional DC motor in railway switch. Second, the whole design scheme and key technology of control system is put forward based on analyse of the technical parameters and requirements. Then the whole system has been designed in detail according to five circuit function modules respectively: main power and drive circuit, PWM and logic synthesize circuit, forward & reverse auto recognize circuit, high-frequency DC/DC switching-mode power supply and protection against lightning strike of system. Finally, a prototype instrument is developed, the experiments of switching-mode power supply and BLDCM are accomplished and experimental results and its analysis are also presented.It can be seen from experimental results, that the control system reaches all the qualities required by the railway point switch. The motor starts fast and operating well in forward and reverse working condition, at the same time, it has higher efficiency and has more powerful protections against electromagnetic interfere and lightning strike. The technology is used not only in the railway switch but also can be used in other drive control equipments and has extensive prospect.