Modeling the Combination Wave Generator (CWG)
The standards describe the waveshape associated with a lightning surge. But they make no mention of how to design the piece of equipment (the CWG) which will have the required characteristics. The required waveshapes were described in Fig. 11.1. The problem is that one of them is an open-circuit voltage waveform, one a short-circuit current. Neither is realistic because we intend to connect a nonzero, noninfinite circuit impedance across the terminals of the CWG. We have to account for the 42-Ω resistive impedance in series with the DUT/EUT. In this particular application, 2 Ω out of the total 42 Ω is expected to come from the CWG.
The actual rise time of the waveform in our application is neither ...

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