Jiannian Dong

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.

Analysis for temperature field and thermal stress of the pulsed inductor

The pulsed inductor is a key device in the pulse power supply in electromagnetic launch and electromagnetic propulsion systems. With the requirements of the weaponization of pulse power supply, whether the continuous pulse discharge can be realized is an important criterion for testing the performances of the pulse power supply. During the continuous pulse discharge, the temperature distribution and the thermal stress are created in the pulsed inductor when the electric current flows and greatly affect the efficiency and the mechanical structure of the pulsed inductor. The objective of this paper is to investigate the effects of the temperature distribution and the thermal stress on pulsed inductors. First, by using the finite element method, the theoretical calculation for the temperature distribution is provided. Next, the experiment of studying the temperature distribution of the pulsed inductor is designed; the thermocouple is used to measure the temperature generated during the pulse discharge to show the reasonability of simulation results. Based on the aforementioned results, the theoretical calculation for the thermal stress is given. This study will help to improve the mechanical structure design and the performance of the pulsed inductor.

A 600kJ Pulsed Power Supply for Electromagnetic Launching Application

The impulsive acceleration of active protection elements can preferably be realized by single-stage electromagnetic launcher systems using pancake coils1. In order to produce time varying magnetic field, during the year 2004, a pulsed power system with two modular structured energy packs (300 kJ) has been built up as a basic facility for testing pancake coils systems. Each power supply module comprises 6 capacitors, an improved spark gap switch adapted to 200 kA discharge current, a crowbar diodes, a high frequency PWM rectifier and a well-designed coaxial power line serving as a pulse-forming network Two modules can be triggered independently by controller with fiber optic transmitters. The selection of the launch direction can be changed by a short delay (a few microseconds to 10 millisecond) between the trigger pulses. In order to reduce influence of electromagnetic interference and electromagnetic force and provide high flexibility reliability, we have improved the arrangement of components and structure of pulsed power module. Two modules are designed for a maximum charging voltage of 7 kV and peak current up to 200 kA per module. The paper presented here describes the test facility and the prototype arrangement of launcher system with two assembled pancake coils fed by two of the modular pulsed power supply units described above. Further, the investigations and results will be presented.

Analysis for Temperature Field and Thermal Stress of the Pulsed Inductor

The pulsed inductor is a key device in the pulse power supply (PPS) in electromagnetic launch and electromagnetic propulsion systems. With the requirements of the weaponization of PPS, whether the continuous pulse discharge can be realized is an important criterion for testing the performances of the PPS. During the continuous pulse discharge, the temperature distribution and the thermal stress are created in the pulsed inductor when the electric current flows, and these greatly affect the efficiency and the mechanical structure of the pulsed inductor. The objective of this paper is to investigate the effects of the temperature distribution and the thermal stress on pulsed inductors. First, by using the finite-element method, the theoretical calculation for the temperature distribution is provided. Next, the experiment for studying the temperature distribution of the pulsed inductor is designed; a thermocouple is used to measure the temperature generated during the pulse discharge to show the reasonability of simulation results. Based on the aforementioned results, the theoretical calculation for the thermal stress is given. This paper will help to improve the mechanical structure design and the performance of the pulsed inductor.

Simulation of the Pulsed Power Supply Module Based on Electromagnetic Structure Coupling

It is important to analyze the electromagnetic coupling characteristics in pulsed power supply (PPS) during the design, and electromagnetic force analysis is becoming more and more important with the development of large capacity and miniaturization of PPS module. In this paper, the magnetic force on the metal structure affected by the pulsed electromagnetic field of the reactor is analyzed and calculated by the means of the finite-element code ANSYS. The results show that the electromagnetic force on the metal structure near the reactor is about ten times that of other parts. The eddy current distribution is calculated by the electromagnetic coupling simulation while the stress on the metal frame is analyzed by the electromagnetic structure coupling simulation. The breaking point assumed to be the weakest point in the structure. The weakest point in the structure is indicated by structural stress simulation. The electromagnetic force is reduced by cutting off the main induce loop through simulation, and the eddy current is measured by experiments.

Thermal Performance Study on Pulsed Inductor

Based on the features of large heating power per unit volume and small cooling surface area, the thermal management is one of the key technologies and plays a significant role for the pulsed inductor. A mathematical model which describes the heat transfer and thermal accumulation processes with the operating condition of periodic pulse loading for the pulsed inductor has been developed and validated in this paper, the model results show a fine accuracy as compared with the test data. In addition, a computer code has been implemented to simulate the thermal accumulation and performance of natural cooling with different operating conditions (as the various of pulse voltage, pulse spacing and pulse duration). The thermal performance study indicates that the pulse voltage, pulse spacing and pulse duration are the focus factors to the thermal accumulation for the pulsed inductor, and the effect of the natural cooling by surface area of the inductor is poor under the periodic pulse loading.

Thermal performance study on pulsed inductor

Based on the features of large heating power per unit volume and small cooling surface area, the thermal management is one of the key technologies and plays a significant role for the pulsed inductor. A mathematical model which describes the heat transfer and thermal accumulation processes with the operating condition of periodic pulse loading for the pulsed inductor has been developed and validated in this paper, the model results show a fine accuracy as compared with the test data. In addition, a computer code has been implemented to simulate the thermal accumulation and performance of natural cooling with different operating conditions (as the various of pulse voltage, pulse spacing and pulse duration). The thermal performance study indicates that the pulse voltage, pulse spacing and pulse duration are the focus factors to the thermal accumulation for the pulsed inductor, and the effect of the natural cooling by surface area of the inductor is poor under the periodic pulse loading.

Simulation of electromagnetic force between pulsed inductor and internal structure of power supply module

With the development of electromagnetic launch (EML) technology, the pulsed power supply (PPS) module applied in EML needs to be smaller, lighter, and more compact. Electromagnetic force (EMF) is one of the most serious problems when PPS module works with high current. In this paper, we study the PPS module used in EML technology. The pulsed inductor model is built based on structure characteristics. The distribution of current density in the inductor during discharge is analyzed. The finite element analysis software is used to simulate and analyze the characteristics of the induction current and the EMF. The simulation model is composed of inductor and metals structures. The EMF laws are put forward by simulation of different shaped metals at different positions. By analyzing the distribution of the eddy current and EMF on the metal conductors at different positions, the EMF laws between the inductor and metal conductors in PPS module are presented in this paper.

A type of trigger system for electromagnetic rail gun

In this paper, a type of trigger system for electromagnetic rail gun was reported. The power supply of Electromagnetic-launch-system was achieved by pulse discharging of capacitor, it had the characteristic of high voltage and huge current, so a reliable measure-and-control system was necessary to avoid the danger and to insure the predetermined power supply touching off according to the predetermined time sequence. We use serial communication for its characteristic of low cost and easy maintenance, and transmitted signals by optical fiber between master computer and terminal because of the very strong electromagnetism disturbing. The trigger in power supply employed synchronous optical coupling technique and transformer isolation drive to insure touch off safely and anti-interference ability.