Design and implementation of DC-to-DC converter topology for current regulated lightning generator

Abstract

When aircraft are impacted by lightning strikes, structural fuselage and components are stressed by electric and thermo-mechanical constraints, which impose a need for reliable experimental test benches to design accurate and enhanced lightning protections. The aim of this work is to investigate, design and compare different topologies of DC high-current generators in order to experimentally reproduce the continuous lightning current waveform component applied to produce an electric arc up to 1 meter long. An electrical model of a standard lightning C*-waveform for 1 m long arc is set, leading to an equivalent resistor varying from 4 to 8 Ω. This model enables a theoretical comparison between the DC/DC converters Buck and Buck-boost topologies to generate such a current-regulated waveform through a load using a capacitor bank and applying a minimum initial stored energy criterion. The experimental implementations of Buck and Buck-boost configurations are designed and tested. Optimizations about the accuracy of the current regulation through feedback loop and the respect of components operating electrical and power parameters are presented. In particular, the implementation of a snubber filter and a frequency control of the switching operations, which are mandatory elements in the operation of DC converters, are described to prevent the circuit from damaging initiated by transient overvoltage peaks. Both Buck and Buck-boost configurations are experimentally implemented to perform a standard C*waveform through a 4 Ω resistor and the Buck configuration proves ability to generate electric arcs up to 1.5 m respecting the standard aeronautic waveform of lightning.

Development of a low voltage railgun in the context of a swept lightning stroke on an aircraft

“…Indeed, the copper wire is less resistive than the electric arc -90 mΩ for the copper wire compared to around 0.5 to 1 Ω for 25 cm of a 400 A electric arc. 45 In Figs.…”

“…Figure 19 presents the configuration of the electrodes where the electrode above is a rod of tungsten of 10 cm diameter with a dielectric diverter ball at the tip, and the electrode below is an aluminum plate. The lightning generator is able to reproduce a C*-lightning waveform electric arc as recommended by the lightning standard (ARP5412A 2013): 44 The generator produces an electric arc that can be extended to more than 1 m with a current shape of 400 A ± 10% during 100 ms. 45 The initial distance between both electrodes is set at 50 cm and centered in the projectile axis so that the plasma jets in the vicinity of the electrodes do not affect the interaction of the electric arc and the test plate during the lightning strike. Since, during the strike, the electric arc is able to be elongated to more than 1 m, the inter-electrode electric potential can reach up to 2 kV.…”

Physical properties of the swept arc channel in the context of lightning strikes to aircraft

“…The lightning arc generator used in this work is capable of producing electric arcs of up to 1.5 m with a current regulation of 200-800 A, respecting the C * standard aeronautical lightning waveform described in SAE ARP5412B [4] and ED 105A [26]. It is described in Andraud et al [24].…”

“…The arc ignition phase. As described in Andraud et al [24], the lightning arc is simulated with an indirect electrode configuration and thus an ignition wire of copper is used. This configuration is recommended by the standard guideline document ED-14E [28].…”

“…To establish a relevant experimental database fulfilling the scientific needs, the present study uses the experimental instruments developed in two recent papers: a DC lightning generator [24] and a railgun electromagnetic launcher [25]. These two instruments are coupled to reproduce a sweptstroke experiment.…”