Development of a 0.6-MV ultracompact magnetic core pulsed transformer for high-power applications

The generation of high-power electromagnetic waves is one of the major applications in the field of high-intensity pulsed power. The conventional structure of a pulsed power generator contains a primary energy source and a load separated by a power-amplification system. The latter performs time compression of the slow input energy pulse and delivers a high-intensity power output to the load. Usually, either a Marx generator or a Tesla transformer is used as a power amplifier. In the present case, a system termed “module oscillant utilisant une nouvelle architecture” (MOUNA) uses an innovative and very compact resonant pulsed transformer to drive a dipole antenna. This paper describes the ultracompact multiprimary winding pulsed transformer developed in common by the Université de Pau and Hi Pulse Company that can generate voltage pulses of up to 0.6 MV, with a rise time of less than 270 ns. The transformer design has four primary windings, with two secondary windings in parallel, and a Metglas 2605SA1 amorphous iron magnetic core with an innovative biconic geometry used to optimize the leakage inductance. The overall unit has a weight of 6 kg and a volume of only 3.4 L, and this paper presents in detail its design procedure, with each of the main characteristics being separately analyzed. In particular, simple but accurate analytical calculations of both the leakage inductance and the stray capacitance between the primary and secondary windings are presented and successfully compared with CST-based results. Phenomena such as the core losses and saturation induction are also analyzed. The resonant power-amplifier output characteristics are experimentally studied when attached to a compact capacitive load, coupled to a capacitive voltage probe developed jointly with Loughborough University. Finally, an LTspice-based model of the power amplifier is introduced and its predictions are compared with results obtained from a thorough experimental study

Temperature dependence of Kerr constant for water at 658 nm and for pulsed intense electric fields

The temperature dependence of the Kerr constant for water has been determined over the range 19 °C-45 °C at a wavelength of 658 nm. This paper presents the experimental arrangement used for this purpose and the data obtained, for which a polynomial fit is provided. A formula is also suggested to help estimate the variation of the Kerr constant for water with both temperature and wavelength

Determination of breakdown voltage along the surface of a cylindrical insulator

This paper investigates the electric breakdown along the surface of a cylindrical dielectric, part of a coaxial transmission line. The particular geometry of the insulator is very common, as it is used at the input or output of most high-power, high voltage generators. The streamer propagation criterion is used to calculate the flashover voltage. Studies of the dependence of the flashover voltage on the distance between the electrodes obtained in tests with DC voltage and also by applying voltage impulses with different durations and rise-times are reported. The highest difference between the estimated values and the experimental data is less than 15%, which proves the applicability of the criterion for determining the surface breakdown voltage within the geometry under study. In particular, the results of these studies are used in the design of a compact 0.5 MV pulsed power system currently under development

Demonstration of a novel pulsed electric field technique generating neither conduction currents nor joule effects

This paper is devoted to a detailed presentation of all aspects involved in a demonstration of a novel pulsed electric field (PEF) technique that does not generate neither conduction currents nor Joule effects. Details are given of both the experimental arrangement and the electro-optic Kerr-effect-based diagnostic used in the measurement of the intense PEFs in water. The results show unequivocally that the novel technique is effective in significantly reducing the initial concentration of Escherichia coli bacteria. Finally, a brief comment on the way ahead is provided. © 2013 IEEE

Theoretical and experimental studies of off-the-shelf v-dot probes

This paper introduces the work undertaken to reliably use off-the-shelf differentiating voltage probes attached to coaxial transmission lines. The results obtained prove that indeed such probes are a valid and simple instrument for measuring nanosecond and subnanosecond voltage impulses. As a bonus, this paper also highlighted an important challenging phenomenon that appears whenever an attempt is made to measure fast voltage impulses with a differentiating probe positioned too close to the closing switch of a pulse forming line generator

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 reported previously. 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 the paper, together with results obtained from full scale tests