The Development Of DC Chopper And Its Control System

The developing economy, the increasing urban population, the shortage of energy and the deteriorating environment make the importance of urban transit stand out more and more. DC driving plays an important role in electrical driving system of urban railway. To satisfy the requirement of today's urban railway DC driving system, This paper developed a DC chopper with great volume as 270KVA which can guarantee the DC driving vehicle is stably operated with good running performance under driving, resistance braking and feedback braking working condition. The A-type two quadrants DC chopper was adopted for the main circuit of the chopper developed by this paper. The IPM integrated with over-voltage prevention, over-current prevention, over-temperature prevention and driver was used as the chopping module. The control circuit(controller) of the chopper was dominated by two MCUs, one was responsible for communication with upper control system to meet the BUS control demand of modern railway vehicles, another was in charge of real time control of chopper and data acquisition and data showing as well. AT89S52 was selected to serve as the former, and 80C196K.C the latter. They shared a dual port RAM as a common database. The setting of working conditions was achieved by the HSI ports of 80C196KC and the chopper was controlled by the signal outputted by HSO and I/O ports of 80C196KC too. What's more, the showing circuit, prevention circuit and sampling circuit were designed on the same board properly.The chopper was ruled by the controller with the method of instantaneous current. The main task of the program of AT89S52 was to assure the precision the communication with upper control system. The main program of 80C196KC received the working condition and prevention request by interrupting mode. In the interrupting service caused by working condition, the inquiring mode was used to distinguish which one caused the workingcondition interrupting service, then, calling the corresponding interrupting service. The instantaneous current subroutine used current increment as a rule which decide to accept the sampled current data or not and controlled the chopper based on the validities.On the series motors testing bed, adapted from separately excited motors. The three working condition of chopper and series motors were tested individually and the feedback braking condition was simulated by energy self-circle successfully.