Frequency response analysis of a Rogowski coil transducer for railgun pulse current measurement

Some of intriguing advantages of Rogowski coils, such as high bandwidth, capability of measuring large currents, non-saturation and potential-free, make it possible to detect and diagnose large pulsed current from an electromagnetic launch system. In this paper, high frequency behavior for a Rogowski coil is analyzed. Considering the model of the coil frequency response, a design method for the transducer is presented. The damping ratio, based on termination resistors, can divide the whole frequency band of the coil into three sub-bands, i.e. derivation band, proportion band and resonance band. Therefore, the corresponding outside integrator circuit is built based upon the characteristics in each sub-band. A novel compound integral circuit is, then, described, which consists of self-integral, passive RC integral and active RC integral. This compound integrator improves the transducer measurement´s upper bandwidth limit around the coil natural frequency. Finally, a coil of 100 turns is constructed using compound integrator of 20Hz~2.0MHz and sensitivity of 1mV/A. Simulation and experimental results verify that the transducer can operate within both the measurement bandwidth of power grid current and the railgun discharging current from the pulse forming unit.