Dai Ling

Design and Construction of a Trigger Generator Based on Pulse Transformer for Spark Gap Switch

A two-electrode graphite spark gap switch is used as the main discharge switch and triggered by a reliable trigger generator in a pulsed-power conditioning system. The trigger generator based on resonant charging of a pulse transformer is constructed. An appropriate ratio can be obtained when using resonant charging based on a core-type pulse transformer. The charging time is dependent on the leakage inductance and the capacitance of the primary and secondary capacitors. The stray resistance and magnetizing inductance of the resonant charging circuit have an impact on ratio and energy transmission efficiency. A dry-type pulse transformer with a load of 1.08 nF, an output voltage of more than 130 kV, and a winding ratio of 65 is presented. A self-breakdown three-electrode output switch is used to shorten the rise time of the output impulse. The deviation of the self-breakdown voltage of the self-breakdown three-electrode output switch is much smaller than that of the self-breakdown two-electrode output switch. It assures that the trigger generator has a low jitter of output impulse when a lot of energy modules work simultaneously. The output impulse of the trigger generator with a peak value of more than 120 kV and a rise time of less than 30 ns can trigger the two-electrode graphite spark gap switch reliably.

Analysis of Electric Parameters of a PPS System and Their Influence on Muzzle Velocity in Electromagnetic Railguns

A 500 kJ compact pulsed power supply (PPS) system used for electromagnetic railgun (EMG) system has been developed to investigate the influence of electric parameters on muzzle velocity in the paper, from which the stability and reliability of the PPS system can be evaluated. The pulsed power supply system consists of ten modules, and each module is composed of a high energy density capacitor, a triggered vacuum switch, a pulse shaping inductor, a dump resistor and a crowbar. Influence of different parameters on the velocity was analyzed by ATP simulations in this paper. The parameters include capacitance, equivalent series resistance (ESR) of the capacitor, inductance, natural electric parameter and jitter time of the TVS. The ESR and natural electric parameters are critical influencing factors by comparing the simulation and experimental results. In the end, muzzle velocity deduced by the current, which is obtained from a new model of actual circuit, is about twenty percent lower than that in ideal condition. It is pointed out that the velocity error is mostly caused by ESR and natural electric parameter.

Study on Triggering Characteristics of High Current Triggered Vacuum Switches

High current switch is a key component of a pulsed power source. Triggered vacuum switch (TVS) possesses many advantages including wide range of operating voltage, compact structure, low cost and so on, so it is considered as one of the most compelling switch in pulsed power system. This paper describes two types (A and B) of TVS samples with different main electrodes and triggering electrodes. Based on theoretical analysis and experimental results, the triggering characteristics of TVS samples have been researched. The triggering polarity, triggering energy and operating voltage influence the triggering delay and the jitter of delay. To recover the failure of TVS samples caused by decreased triggering energy, series air gap was tried. In the lifetime test, the resistance between the triggering electrodes dropped gradually, leading to the failure of TVS. Both types of TVS have discharges number of 100 shots with 70 kA peak current. The ablation on the main electrodes of type B TVS was slighter than that of type A.High current switch is a key component of a pulsed power source. Triggered vacuum switch (TVS) possesses many advantages including wide range of operating voltage, compact structure, low cost and so on, so it is considered as one of the most compelling switch in pulsed power system. This paper describes two types (A and B) of TVS samples with different main electrodes and triggering electrodes. Based on theoretical analyis and experimental results, the triggering characteristics of TVS samples have been researched. The triggering polarity, triggering energy and operating voltage influence the triggering delay and the jitter of delay. To recover the failure of TVS samples caused by decreased triggering energy, series air gap was tried. In the lifetime test, the resistance between the triggering electrodes dropped gradually, leading to the failure of TVS. Both types of TVS have discharges number of 100 shots with 70kA peak current. The ablation on the main electrodes of type B TVS was slighter than that of type A.

Development of a 500kJ Pulsed Forming Network for EML System

Summary form only given. The paper describes a capacitor-based pulsed forming network (PFN) with a compact design as the primary means of energy storage and pulse shaping for electromagnetic launcher system. The network consists of ten 50kJ modules and can supply various shapes of high current pulse by change of charging voltage and firing time of each module. The maximum current for each module is 70kA at the charging voltage of 13kV. The critical components in the PFN are discussed, including high energy density capacitors, inductors, discharge switches, crowbar diodes and dump resistors. The basic technical requirements to be fulfilled by these components are presented. The discharge switch is very important to the PFN. Characteristics of triggering, life and reliability of gas switches and triggered vacuum switch (TVS) are compared through a lot of tests in PFN. The experiments of the paralleled modules with 592muF capacitor, 20muH inductance, 30mOmega dump resistor and similarly short load were performed. The total output current was 409kA.

Study on uncoupling characteristics of foil wire in metallized capacitors

Safety electrode can protect metallized capacitors from catastrophic breakdown. It plays a role in second protection which would help the metallized capacitors achieving better self-healing. The purpose of this paper is to analyze the disconnection mechanism of the small fuse of T-polypropylene safety foil, the energy of disconnecting the fuse in different width, and the relationship between the broken-down energy and time. The results of experiments indicate that the disconnection of fuse is caused by the small crack in fuse which is brought by the current heat, and the metallized layer will be evaporated as the crack becomes long enough to generate creeping discharge. The disconnection of different width fuse has little relationship with the thickness of polypropylene, but has clear relationship with the square resistance. The energy of disconnection will decrease with the increase of the time while current flows through the fuse.