G. Louverdis

Transportable high-energy high-power generator

High-power applications sometimes require a transportable, simple, and robust gigawatt pulsed power generator, and an analysis of various possible approaches shows that one based on a twin exploding wire array is extremely advantageous. A generator based on this technology and used with a high-energy capacitor bank has recently been developed at Loughborough University. An H-configuration circuit is used, with one pair of diagonally opposite arms each comprising a high-voltage ballast inductor and the other pair exploding wire arrays capable of generating voltages up to 300 kV. The two center points of the H configuration provide the output to the load, which is coupled through a high-voltage self-breakdown spark gap, with the entire autonomous source being housed in a metallic container. Experimentally, a load resistance of a few tens of Ohms is provided with an impulse of more than 300 kV, having a rise time of about 140 ns and a peak power of over 1.7 GW. Details of the experimental arrangement and typical results are presented and diagnostic measurements of the current and voltage output are shown to compare well with theoretical predictions based on detailed numerical modeling. Finally, the next stage toward developing a more powerful and energetic transportable source is outlined.

2D Modelling of Skin and Proximity effects in Tesla Transformers

Tesla transformers find a wide range of applications from particle accelerators to HPM generators and compact repetitive EMP generators. Their design and analysis require detailed numerical modelling, particularly when the system is housed in a metallic cylindrical container. The paper presents a numerical modelling technique which allows the very accurate calculation of the resistance and inductance of the transformer, taking into account the magnetic diffusion process that gives rise to skin and proximity effects, and all the magnetic interaction between components affecting the system performance.

Transportable High-Energy High-Current Inductive Storage GW Generator

A number of high-power applications require a transportable high-energy, high-current GW generator to drive a pulsed power system at the output. A first prototype, based on exploding wire technology and using an H-bridge circuit configuration, was developed at Loughborough University a few years ago and has been previously reported. The present stage of the work has necessitated the development of a more powerful and energetic source, and this is now based on inductive storage technology. A 400 kJ capacitor bank is connected by a high-Coulomb explosively driven closing switch with an air-cored 0.6 MV transformer, an exploding wire array, and a high-power diode based on a polarity-dependent spark-gap completing the arrangement. The GW generator, including the command and control module, is accommodated in two ISO containers. The various components of the generator are described in this paper, together with results obtained from full-scale tests.

Coaxial 0.5 MV air-core pulse transformer

The paper describes the successful development of a novel design of high-voltage pulse transformer, having a coaxial primary winding and a toroidal secondary winding and a magnetic coupling coefficient between the windings in excess of 0.8. The air-core transformer operates in air, does not require any oil or pressurized gas, and it is capable of producing high-voltage impulses in excess of 0.5 MV with a corresponding load power of several GWs.

A mobile, high-power, high-energy pulsed-power system

A high-power, high-energy pulsed-power generator, based on a 415 kJ / 22 kV capacitor bank, has recently been developed and tested indoor at Loughborough University. The generator can drive a high-impedance system, generating a total electrical power of many GW while depositing Joule energy of many tens of kJ. The arrangement is based on inductive storage technique that includes a 600 kV high voltage transformer, two closing switches and an opening switch. The high-Coulomb closing switch in the primary circuit is activated using detonators while the closing switch, mounted in the secondary circuit to condition the load output, uses a high-pressure gas self-breakdown closing switch. The opening switch in the primary circuit is an exploding wire array made from thick copper wires fired in quartz sand. Recently the entire system, including its command and control unit, was mounted into two ISO containers powered by diesel generators. The paper will describe the resulting mobile system and provide details of its performance capabilities.

A low-energy, flexible pulsed-power generator for general purpose indoor and outdoor experimentation

An autonomous, compact and repetitive pulsed power generator has recently been developed at Loughborough University for use in low-energy, general-purpose experimentation, in either indoor or inclement outdoor environments. Flexibility, reliability and safety were the most important design requirements, which were achieved through the use of interchangeable components, off the shelf units and the development of a fibre-optic controlled charging and triggering system that allows the complete system to run from a single battery source. The present arrangement is based on a General Atomics 1 µF capacitor although many GAEP S/SS and SE/SSE series capacitors are compatible. A Trigatron discharges the capacitor into a transmission line with series connected mounting bays designed to accommodate a range of resistors or inductors if required. A high-voltage coaxial cable connects the generator to an external load or a further pulsed power system. Current and voltage are internally monitored using a Pearson current transformer and a Tektronix high-voltage probe. The completed system is housed in a weatherproof metallic container and mounted on rubber wheels. To date it has been operated successfully on more than 100 occasions, both in the laboratory and in various outdoor conditions.

A high-power, high-energy pulsed-power generator for high-impedance loads

A high-energy pulsed-power generator, based on a 415 kJ / 22 kV capacitor bank, has recently been developed and tested at Loughborough University. The generator can drive a load having a resistance of between 10 Ω and 40 Ω and a self-inductance between 10 µH and 30 µH, using conventional inductive storage techniques that include a high-voltage transformer (HVT) with a coupling coefficient of about 0.8 and capable of withstanding up to 600 kV. An exploding wire array (EWA) is used as an opening switch in the primary circuit and a self-breakdown closing switch (operating under pressurised SF6) is implemented in the secondary (load) circuit to condition the output,. The bank discharge is controlled by a detonator-activated dielectric breakdown, high-coulomb, low-inductance closing switch.

High-voltage pulsed-power sources for high-energy experimentation

A high-energy pulsed-power source based on a 30 kJ capacitor bank has recently been developed at Loughborough University. An H-bridge circuit configuration is used, with one pair of the diagonally opposite arms comprising a high-voltage ballast inductor and the other pair an exploding wire array capable of generating voltages up to 250 kV. The two centre points of the H-configuration provide the output to a high-power resistive load, which is coupled through a high-voltage self-breakdown spark gap. A resistive load of 80 Ω is provided with a 300 kV impulse with a rise time of about 140 ns and a peak power of about 1 GW. Following the successful testing of the power source under indoor laboratory conditions, a similar transportable source was constructed. This is presently housed in a metal container, with the load fed through a pair of 25 m long high-voltage cables. Due to improvements in the exploding wire arrays arrangement, each now generating about 300 kV, the source is capable of delivering a power of 1.7 GW to a 45 Ω load. The Joule energy deposited of about 3 kJ represents 10% of the energy initially stored in the capacitors. The design of a more powerful transportable source, presently under construction and based on a 400 kJ capacitor bank will also be presented. This source, using an exploding wire array in the primary circuit of a high-voltage transformer, is predicted to be capable of generating in resistive loads an electrical power in excess of 4 GW.