Indirect Lightning Testing using Waveform 3
RTCA/DO-160 and EUROCAE ED-14 section 22 describe testing of indirect lightning into cable bundles using waveforms derived from high energy fields caused by waveform D lightning transients in the vicinity of an aircraft. Waveform 3 frequencies depend upon the length of the system and the length of the cables. Longer cables can sustain only lower frequency oscillations (inversely proportional to length). Standard requirements are for waveform 3 1MHz and 10MHz to give the same current response into low impedance cable bundles. However, for technical reasons it is (nearly) impossible to build a waveform 3 (WF3) generator for 1MHz and 10MHz having the same source impedance and delivering the cable bundle limit current required. This paper will discuss reasons why the 10MHz generator source impedance is higher than for 1MHz, what the consequences are for WF3 limit current and how this influences the design of a suitable waveform 3 impulse generator.
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