Shizhong Li

Analysis of Energy Conversion Efficiency of a Capacitor-Based Pulsed-Power System for Railgun Experiments

To analyze the stored-to-kinetic energy conversion efficiency, a transient electric-circuit model for a railgun system is built using the electrical circuit analysis software SIMPLORER in this paper, and the electric parameters of the model are defined with measurement values of the actual system. Many results of simulations and experiments are also presented, and the results show that the equivalent series resistance of the coaxial cables and the rail resistance are major factors on the energy conversion efficiency. In the end, some methods are proposed to improve energy conversion efficiency of the pulsed-power supply system.

Design and Testing of a 10-MJ Electromagnetic Launch Facility

For basic research on electromagnetic launch technology, the Beijing Institute of Special Electromechanical Technology has initiated a program focusing on the design and testing of a 10-MJ electromagnetic launcher facility with the cooperation of Nanjing University and the Institute of Electrical Engineering, Chinese Academy of Sciences. The facility will consist of a 10-MJ prime energy, a 6-m-long railgun, and a control system. A 3.2-MJ pulse power unit (PPU) with 32 100-kJ modular PFN units has been completed and tested, and its prime energy can be easily extended to 10 MJ. A 6-m-long railgun has been built, which can be easily cut into a 4-m-long railgun by which many firings have been done with the new PPU. Construction and testing of the whole facility are being continued.

The 100-kJ Modular Pulsed Power Units for Railgun

A 3.2-MJ pulsed power supply system for railgun has been built. The power supply system consists of 32 pulse forming units (PFUs) of 100 kJ each. Each PUF can be triggered and controlled independently by the center computer by fiber optic transmitters. The maximum total current of the 3.2-MJ supply system reaches 500 kA. The new PFU is smaller than the former one. The PFU is composed of two capacitors, a set of semiconducting switches (thyristor and crowbar diode), an inductor, a safety device, a local controller and data acquisition circuit, a current coil, and coaxial cables. The modular PFU is designed for a maximum charging voltage of 10 kV and the peak current up to 50 kA/module. In order to reduce the influence of the electromagnetic interference and the electromagnetic force and to provide the high flexibility reliability, the arrangement of components and the configuration of the pulsed power module have been improved. A local data acquisition circuit in each PFU can record and save the discharging current and the voltage of the capacitor itself and upload test data to the computer by fiber optics. This paper describes the stack configuration, the test facility, and the prototype arrangement of 32 modular pulsed power units.

The Development of EML Technology in China

Humans are always making great efforts to make the launch weapons with further range, higher powerful energy, more accurate and controllable abilities. According to the history of launch technology, the paper classifies it into four phases, which are the biologic, mechanical, chemical and electromagnetic launch phases. The analysis shows us the development trend of launch technology, and advantages of electromagnetic launch technology are also declared. Recently, China pays great attention to new technology areas, especially for the EML technology, and the programs of China are mainly focused on the fundamental research. The papers published from the 12th symposium to 16th symposium suggest that there are much more programs for the electromagnetic launch research. The researches of china are also shown in this paper.

Development of a Capacitive Pulsed Power Supply for High-Current High-Velocity Sliding Electrical Contact Studies

A pulsed power supply of a 1.5-MJ capacitor bank has been developed for high-current high-velocity sliding electrical contact studies in railgun launches. The system consists of 8 small modules, each with a capacitance of 15 mF, and one large module with a capacitance of 54 mF. All of nine modules use triggered spark gaps as the main switches. Various shapes of high-current pulse can be formed by controlling the charging voltage and firing time of each module. The small module has been designed for the maximum operating voltage of 5 kV, the peak current of 140 kA, the pulse rise time of 0.9 ms, in which semiconducting diode stack is used as crowbar switch. Since the large module has no crowbar switch and relatively small pulse forming inductance, it can supply high-amplitude oscillating current waveform. The effects of the large module are threefold. First, the large module provides a basic current on which the currents of small modules superimpose to form a nearly constant driving current of armature. Second, the oscillating nature of the current can drastically reduce the muzzle arc current; hence suppression of the muzzle arc can be obtained. Third, the crowbar switch can be removed and therefore the cost of the system can be reduced. The experiments were performed to verify the operation performances of the two kinds of modules, where the modules were discharged simultaneously and/or sequentially. The feasibility of large module on the muzzle arc control is also examined. The results of the experiments show that a total current of 400 kA with a 1.5 ms flat-top time can be obtained and all the modules show good performance during the railgun firing.

The development of EML technology in China

To make launch weapons with further range, higher energy density, better target accuracy, and better control ability are the aims pursued by people for many years. This paper divides the history of launch technology into four stages, which are the biologic, mechanical, chemical, and electromagnetic launch stages. The development trend of the launch technology is discussed, particularly the advantages of the electromagnetic launch (EML) technology. Recently, China has paid great attention to many new technical fields, such as the EML technology. Chinas programs are mainly confined to fields of basic research, which are collected together in this paper. However, the numbers of papers published from the 12th symposium to the 16th symposium suggest that there are more and more programs in the EML field.

Study on the compilation of firing tables for electromagnetic launching interception system

This paper introduces electromagnetic launching interception system (EMLIS), and defines a new format of firing tables according to the characteristics of the system. The paper compiles the firing tables by a lot of launching experiments. The EMLIS can intercept target successfully using the firing tables. So it is proved that the new format of firing tables is suitable for the EMLIS.

Energy Conversion Efficiency of Electromagnetic Launcher With Capacitor-Based Pulsed Power System

The stored-to-kinetic energy conversion efficiency of railgun system is investigated by simulation and experiment methods. There are many factors, which might affect the conversion efficiency of the railgun system. These factors include the parameter values of pulsed power supply (PPS), the velocity of armature, the inductance gradient of rail, and so on. To analyze the stored-to-kinetic energy conversion efficiency, a novel electric circuit simulation model for the railgun system is built. The simulation results show that the less resistance, the more inductance of PPS, the more inductance gradient of launcher, and the higher muzzle velocity of armature can improve the energy conversion efficiency of the railgun system. Some experimental results with the 6-MJ railgun system at Beijing Institute of Special Electromechanical Technology are also presented in this paper, which can illustrate the correctness of the analysis and the simulation results.

Simulation and Test Study of Bores of Different Structures of Electromagnetic Launcher

Currently, the bore shape in an electromagnetic launcher is usually a rectangle, round, or an inverted arc. A comparison of the current density distribution, induction gradient, moment of inertia, contact pressure, contact state, structure manufacture, and launching precision between the rectangle and inverted arc bore shapes was carried out. We got some results about the effect of bore shape on the electromagnetic launcher. The results show that the inverted arc shape performed better than the rectangle in these areas: current density distribution, induction gradient, moment of inertia, contact state, and the accuracy of armature running.

Simulation and test study on different structure bore of electromagnetic launch

Bores shape in electromagnetic launch usually involves coupled rectangle or quadrate, round and inverted arc at the present. But bores shape of test assembly is major rectangle and inverted arc. In the paper the studies of simulation and test are carried on the bore of rectangle and inverted arc. The detailed comparison about the bore of rectangle and inverted arc were studied in current density distribution, induction gradient, contact pressure, contact state, structure manufacture and launching precision. The last test studies of both bore were carried on contact state and launching efficiency. We got a few of results about the bores shape in electromagnetic launch. The results prove that the bore of inverted arc were better than the bore of rectangle in current density distribution, induction gradient, contact state and the accuracy of armature running. These can be foundation of different need in electromagnetic launch design.