The Design Of DC Circuit Breaker For Subway Locomotive

With the large-scale construction of subway, the domestic subway power system equipment has become a national key research project. Since the subway generally adopts DC power supply system, while the DC circuit breaker in DC power supply system is an extremely important protect equipment, so the development of DC circuit breaker is of great significance.This paper mainly uses the CAE technology to design and simulate the main part of the DC circuit breaker (including the contact system, arc-extinguishing system, permanent magnet actuator and the over-current release). By studying the structure and working principle of the DC circuit breaker, the paper firstly designs the main parameters of the DC circuit breaker, such as material, open distance, pressure, geometry size and overtravel of the contact. According to the characteristics of the DC electric arc, this paper chooses the metal sheet arcing chamber and designs metal sheet, at the same time analyses magnetic field distribution of the arcing chamber when the metal sheet are composed of different materials. This paper calculates the distribution of the electric field of arcing chamber when arc exists in the metal sheets, and passivates the corner of the contact, which can effectively reduce the largest electric field intensity and prevent back commutation phenomenon during the period when arc is burning.Secondly, according to the working principle of the single steady-state permanent magnetism actuator, the single steady-state permanent magnetism actuator has been designed. Through static analysis of permanent magnetic actuator, the closing force is calculated, and the distribution of magnetic field is analyzed when it is in the opening and closing position. The dynamic characteristics of permanent magnetism actuator are calculated to obtain the relationship between suction suffered moving core and time. As the loading conditions, dynamic simulation Adams have been used to create a motion model of virtual prototype, as a result the dynamic characteristics of the DC circuit breaker moving contact are calculated, and the motion curves of the moving contact are obtained. Finally, according to the structure analysis of the over-current release, the open position of the armature is chosen as the design point. The optimize target is to make the volume of armature smallest, and the constraint condition is suction suffered by armature. The First-order optimization method is used to achieve optimize the design of the over-current release. Considering the load current changes with time, dynamic simulation of the optimal designed structure was simulated and the results meet the design requirements of the over-current release.