Effect of Coupling Slot on Measurement Waveform of Rogowski Coil

Rogowski coil is an effective tool, which is capable of testing kilo-ampere (kA)-class nanosecond (ns)-scale pulsed current. The basic principle is the Faraday Law of electromagnetic induction. In practical application, it is found that the test current waveform of a Tesla-type generator via the Rogowski coil is strongly distorted. It is conjectured that the width of coupling slot in the generator contributes to the distortion. A circuit model including the slot of the Rogowski coil is proposed. Via this model, the conjecture about the slot is verified. In addition, it is found that the oscillation superimposed on the measured waveform becomes large as the slot becomes narrow. To further study the effect of the slot width on the measurement waveform, the practical 3-D model of the Rogowski coil assembled on the generator is also established and the oscillation dependent on the capacitance of the slot is obtained. In the end, an empirical formula to design the width of the coupling slot of the Rogowski coil is presented. With this formula, the new width of coupling slot is calculated out and the ideal measurement waveform of the Rogowski coil in the Tesla-type generators is obtained.