Coaxial current transformer for test and characterization of high-power semiconductor devices under hard and soft switching

The use of a coaxial current transformer (CCT) is an interesting choice for pulsed measurement of current through power devices during switching trans ients, The CCT is used to reflect current for convenient external measureme nt with minimal insertion impedance in the critical power circuit. This pap er analyzes the characteristics of the CCT and explains how it can be integ rated into test setups for both press-pack and module packages. Finite-elem ent techniques are applied to the study of the CCT to obtain detailed elect rical and magnetic characteristics. Current distribution in the primary and secondary circuits, flux densities, and insertion inductance and resistanc e are among the design information that can be obtained through finite-elem ent analysis. Analytical and numerical results are obtained for the propose d CCT that is integrated in test setups for MOS turn-off thyristors (press- pack) and high-voltage insulated gate bipolar transistors (module) characte rization.