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Design and development of lightning waveform generators

Leichauer, Philip 2017. Design and development of lightning waveform generators. PhD Thesis, Cardiff University.
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Abstract

Aircraft are struck by lightning approximately once every 10,000 hours each. It is essential that this does not cause them to malfunction or otherwise endanger the craft or passengers. Cardiff University commissioned the Morgan-Botti Lightning Laboratory (MBLL) to perform lightning testing to aid aircraft safety development. The work described in this thesis was undertaken while acting as the engineer and project manager to design, develop and build the laboratory. Its focus was upon ensuring that the lightning test waveforms were delivered, as required by test standards, in the best possible way that was achievable within budget. A lightning test frequently involves 3 waveforms; a high current initial pulse (A, Ah and D waveforms) followed by a trailing component consisting of an intermediate current B waveform and a long DC discharge (C or C* waveforms), as specified in the aeronautical lightning test standard ED84. A thorough understanding of the high current lightning test waveforms was gained by analyzing their mathematical description; this lead to developing A, Ah, D and B waveform generators optimized to make the best use of available equipment and reliably deliver the required waveforms. Many options were considered for generating the C and C* waveforms. Capacitors were chosen on space and safety grounds over other technologies. Two modes of operation were implemented; firstly, a CR discharge where the waveform current sagged over the duration of output and, secondly, a PWM controlled flat discharge using a 3 phase buck converter topology. The decision, mathematical understanding and circuits behind the development of the waveform generators are presented in to facilitate and inform future design of similar waveform generators or test facilities. The laboratory has been operating successfully since 2011 with the D waveform, delivering direct effects lightning testing accurately to international standards. The B and C waveforms were tested successfully in 2014. In the years following, the Ah and A waveforms were implemented as designed also.

Item Type: Thesis (PhD)
Date Type: Submission
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Lightening; Double Exponential; Waveform Generator; Pulsed Power; Capacitor Bank; 3 Phase Buck Converter.
Date of First Compliant Deposit: 29 May 2019
Last Modified: 15 Jul 2019 10:27
URI: http://orca-mwe.cf.ac.uk/id/eprint/122937

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