Performance and Scalability of MJ Sequentially Fired Pulse Forming Networks for Linear and Nonlinear Loads

The principal advantages of the sequentially fired pulse forming network (SFPFN) over its passive analog are its utility in both linear and nonlinear load applications. Operation of the SFPFN consists of charging multiple capacitor banks to different voltage levels and sequentially firing these banks into the load at appropriate times. The load characteristics and the desired pulse attributes determine the module charge voltage and sequential firing schedule. This paper describes the pulsed power system and computer control system design of a 750-kJ SFPFN. Typical experimental results in the case of a linear load are presented and compared with simulations, and pulse-shaping capabilities are demonstrated. Scaling considerations are discussed in the case of increasing the SFPFN energy capacity to 7.5 MJ. The SFPFN uses a computer-controlled field programmable gate array to initiate the trigger signal for each module's output switch. The use of a computer-controlled firing circuit provides an opportunity to incorporate real-time load monitoring and feedback to select the optimal firing times and durations based on dynamic load conditions. The incorporation of feedback during a pulse sequence also allows for the firing sequence to be halted in the event of a fault or other potentially harmful event. The charging controller features a computer monitoring and control system to allow a single power supply to charge multiple capacitor modules by an array of switching relays, even though each module may be charged to a different voltage. In linear load testing, the SFPFN provided a relatively constant current pulse to a resistive load. Pulse-shaping capabilities are demonstrated by varying the charge voltage of individual banks prior to a firing sequence. Future applications of the SFPFN include powering a helical launcher