Effective circuit parameter determination in lightning impulse voltage tests of air core inductors

An effective technique for determination of the circuit parameters in the air core inductor lightning impulse test is presented. The air core inductor is a specific test object affecting the test waveform of which the time to half is often shorter than the standard requirement. To increase the time to half, Glaninger's circuit was introduced by connecting the additional circuit parameters, i.e. the additional inductor and resistor. In order to select the additional circuit parameters and obtain the lightning impulse voltage waveform according to the standard requirement, it is necessary to precisely determine the other test circuit parameters, i.e. the front time resistance, the tail time resistance, parasitic series inductance, and load impedance composing of load resistance, load capacitance, and load inductance. In this paper, the matrix pencil method is employed to determine the circuit parameters by using the recorded waveform from the preliminary experiment. With the known circuit parameters, the additional circuit parameters can be searched to obtain the standard lightning impulse voltage waveform. The proposed method has been verified by some simulation and experimental cases successfully. The proposed technique is very useful in the lightning impulse voltage test of an air core inductor and helps test engineers in design appropriate circuit impedance without a trial and error approach.