The time domain response of BCI transformers

A representative bulk current injection transformer is characterized experimentally in both the time and frequency domains with the goal of quantitatively predicting its time domain response to the trapezoidal pulse specified in MIL-STD 461E. The time domain responses of the representative transformer, as computed from the experimentally obtained frequency domain transfer function and measured directly in the time domain, are in good agreement. We present for the first time a figure of merit, the time-domain pulse injection efficiency, which indicates the fraction of the available pulse energy from the generator that is inductively coupled to a particular structure such as a test fixture. This concept is generalized to the time-gated pulse injection efficiency in order to account for a finite time window. It is seen that about 32.5 percent of the available energy in the trapezoidal pulse is delivered to the test fixture and that of this fraction most (30 percent of the total available energy) is delivered during a 30 nanosecond window, despite the overall extremely long time response of the probe. Finally, frequency domain power efficiency measurements are presented and compared with the time domain pulse injection efficiency.