Investigation of an FCG and pulse transformer based power conditioning system

A cooperative effort was initiated between Texas Tech University and the University of Missouri-Columbia to develop a single-shot power conditioning system to drive an RF load. The purpose of the system is to convert prime power to an output capable of driving a load with an impedance ranging from 15 to 30 Ohms. A Helical Flux Compression Generator (HFCG) was chosen as the electrical energy amplification stage due to its portability and high energy density. Certain topologies of HFCGs are better suited to drive low impedance loads (i.e. short circuits or similar), however, cascaded HFCG systems are capable of driving higher impedance loads, thereby reducing the requirements from subsequent pulse forming stages to match the HFCG output to the load impedance. Therefore, a dual-stage HFCG was chosen to drive a pulse transformer and series fuse in order to produce voltages on the order of 150 kV to 300 kV across the secondary of the pulse transformer. The fuse has been designed to open in 280 ns or less when a peak current of 25 kA-40 kA is reached. The output voltage will be used to drive an RF load or to charge a mesoband oscillator. Both topologies for power conditioning are being considered and tests to date indicate that both types of geometries can be driven by the HFCG and power conditioning system. The results of the experimental tests as well as the energy transfer efficiency will be discussed.

I. Introduction

An HFCG-driven power conditioning system for producing RF radiation has been designed and tested. HFCGs have been used extensively to amplify electrical energy and are attractive as energy transducers in single shot pulsed power systems due to their high energy density and inexpensive fabrication. It is known, however, that mid-sized HFCGs (compressible volume of ~ 300 cm³) are extremely susceptible to typical loss mechanisms such as flux loss, turn skipping, and volume breakdown due to the size and length constraints which are imposed by the overall project design guidelines. Research in developing a mid-sized HFCG manufacturing technique that results in performance that is highly predictable and reproducible from shot to shot is ongoing and progress toward achieving this goal has been reported on previously [1]. The overall goal of incorporating the HFCG into a power conditioning system is the motivation for this research since all components downstream of the HFCG in the power flow must be designed to properly function over a specific voltage and current range. If the voltage and current range can be properly predicted and reproduced, overall system reproducibility will increase and system size will decrease as the components downstream of the HFCG are designed more aggressively.