Quality factor measurements of air-cored solenoids at overtone frequencies

Although Tesla transformers and helical cavity filters are employed in quite different technical areas, a previous contribution demonstrated that applying the techniques used in designing these filters to the secondary winding configurations of a Tesla transformer improved the spectral purity of the output. In the present reported work, measurements of the quality factors of the original and a number of modified secondary windings are shown to provide results at the fundamental and overtone frequencies, thereby illustrating the scale of the possible benefits that can be achieved

Significant practical features of Tesla transformers

Although a large number of publications dealing with Tesla transformers have appeared, many of these are confined to providing an analysis of the transformer performance based on a lumped equivalent circuit model. The present paper is concerned with more practical issues and begins by considering the often overlooked significance of the magnetic coupling between the primary and secondary windings for the range of potential applications of these transformers. It continues by discussing the benefits of using a solid-state primary switch and providing an insight into various other additions that may be made to the basic circuit

Optimizing the secondary coil of a tesla transformer to improve spectral purity

This paper provides an overview of the response of the tuned secondary circuit of a Tesla transformer, following impulse excitation from the tuned primary circuit. Multiorder oscillatory voltages and currents are energized in the secondary circuit, and research is ongoing to determine the fundamental and higher order modes for various secondary winding configurations, with the aim of developing design techniques that can be used to suppress the generation of the higher order modes. It is anticipated that this will lead to generators which exhibit enhanced spectral purity and which will be better suited to use in electronic warfare applications than conventionally wound Tesla transformers. © 2013 IEEE

Improvements to secondary windings of Tesla transformers

Impulse excitation of the tuned primary circuit of a Tesla transformer generates a voltage and current response in the similarly tuned secondary circuit that contains both a fundamental component and a series of multiple higher-order modes. This paper investigates the most significant of these modes, in order to demonstrate a design approach that, when applied to the secondary winding, can bring about a reduction in the higher-order modes without significantly affecting the fundamental term. The resulting process leads to an improved spectral purity of the transformer output, making it better suited than existing conventional designs for application in electronic warfare and other high-power systems

Electromagnetic radiation from a Tesla transformer

In addition to the resistive and dielectric losses that inevitably occur near the secondary winding of a Tesla transformer, electromagnetic radiation into the far field also contributes to the overall power losses and thereby reduces both the effective quality factor (Q) and the power transfer efficiency of this winding. A short study of these effects for a laboratory scale transformer has shown that, in addition to its Q-factor being considerably reduced, the secondary winding is an extremely inefficient radiator of electromagnetic energy

Magnetic coupling in Tesla transformers

Although many publications dealing with Tesla transformers have appeared, most are confined to detailed investigations of the transformer performance based on a lumped equivalent circuit. The present paper differs widely from these in being concerned with the very practical and important issue of the degree of magnetic coupling between the two transformer windings and considers in detail the importance of the coupling factor for a range of applications of these transformers. The constructional features that may be adopted in various practical implementations are explained

MIDOT: A novel probe for monitoring high-current flat transmission lines

A novel inductive probe, termed MIDOT, was developed for monitoring high-current flat transmission lines. While being inexpensive the probe does not require calibration, is resistant to both shock waves and temperature variations, and it is easy to manufacture and mount. It generates strong output signals that are relatively easy to interpret and has a detection region limited to a pre-defined part of the transmission line. The theoretical background related to the MIDOT probes, together with their practical implementation in both preliminary experimentation and high-current tests, is also presented in the paper. The novel probe can be used to benchmark existing 2D numerical codes used in calculating the current distribution inside the conductors of a transmission line but can easily detect an early movement of a transmission line component. The probe can also find other applications, such as locating the position of a pulsed current flowing through a thin wire

Lethality mechanisms in Escherichia coli induced by intense sub-microsecond electrical pulses

In this letter, the authors present the inactivation kinetics of cells of Escherichia coli and its mutants following treatment with high-intensity electrical pulses of 700 and 32 ns durations. Their experimental results suggest that bacterial inactivation by 700 ns pulses is consistent with a mechanism of reversible electroporation, whereas inactivation by 32 ns pulses may occur as a result of damage to intracellular components. They believe that their results represent a first step towards elucidating the mechanism of lethality of submicrosecond pulses of different durations in prokaryotes

Electrode erosion and lifetime performance of a compact and repetitively triggered field distortion spark gap switch

© 1973-2012 IEEE. The electrode erosion and lifetime performance of a compact and repetitively triggered field distortion spark gap switch were studied at a repetitive frequency rate of 30 Hz, a peak current of 8.5 kA, and a working voltage of ±35 kV when the switch was filled with a gas mixture of 30% SF6 and 70% N2 at a pressure of 0.3 MPa. The variations of the time-delay jitter and the self-breakdown voltage were both studied for the whole service lifetime of the spark gap switch. The morphology of both the electrodes and the plate insulator, before and after the service lifetime tests, is also analyzed. The results show that during these tests, the time-delay jitter is basically synchronized with the self-breakdown voltage jitter, and both undergo firstly a process of rapidly decreasing their values, then remaining stable, and finally and gradually increasing after 70 000 pulses. The change in the electrode surface roughness (i.e., surface profile) is caused by erosion and chemical deposits in the switch cavity, which are mainly the two factors that affect the time-delay jitter of the switch. Tip protrusions on the electrode surface, due to electrode erosion, contribute to reducing the time-delay jitter. However, due to chemical reactions, fluorides and sulfides are deposited on the switch components, as well as metal particles caused by electrode erosion sputtering. Slowly, after a large number of shots, all these phenomena affect the self-breakdown performance resulting in an increased self-breakdown voltage jitter, which also causes the time-delay jitter to increase. Although there are a number of reasons that contribute to the deterioration of the performance of the switch, it is fortunate that if a switch suffering a degraded performance is reassembled, with the electrodes mechanically polished and all the components cleaned, the optimal performance of the switch can be restored. If maintenance work is carried out regularly to preserve the condition of the switch's inner components, the service lifetime of the switch can be prolonged

High power RF capabilities at Loughborough University

This is a conference paper. It is also available at: http://ieeexplore.ieee.org/. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.Members of the plasma and pulsed power group at Loughborough University are engaged in several experimental activities related to the generation of high power radio frequency radiation. The paper reviews some of the more important projects that have recently been successfully completed