Analysis and Comparison of Symmetrical Rogowski Coils in High Magnetic Field Environment

Abstract

Summary form only given. Rogowski transducer is a popular method of measuring transient current in pulsed power field due to their significant advantages compared to other current transducers, such as low-cost, easy-modified, whole-range and high-frequency. While the traditional Rogowski coils are unsuitable for measuring the current of compact FCG, especially for the output current, because the compact FCG must be placed close enough to the load to reduce the loop inductance. As a result, the Rogowski coils should be placed close to the stator too. Rogowski coils work by sensing the magnetic field in the space around the conductor on the assumption that the flux in the axis direction contributes none to the output voltage. The assumption is correct in most measuring conditions, except in FCG experiment. Flux compression generator (FCG) is a device in which the chemical energy of explosion transforms into kinetic energy of armature, and subsequently into electromagnetic energy of stator. Recently, FCG is mostly used as a remote current source, so the amplifier rate of the current becomes a critical factor to denote the performance of FCG. But the hostile environment near the FCG experiment will bring great troubles in measuring the input and output current of FCG. To meet the need of current measuring in compact FCG, we manufactured a new current transducer with a symmetrical structure last summer, called symmetrical Rogowski coils, in which two Rogowski coils without return loop were placed symmetrically within framework. According to Ampere's Law, the line integral of the magnetic field around the loop is equal to the current in the loop. As coils are symmetrically combined whose parameters are same, the structure helps to overcome the shortcomings that coils are sensitive to strong magnetic field, which is insurmountable for traditional Rogowski coils o f neither one-layer coils nor two-layer coils. Calibration experiments show that the magnetic field effect has been reduced to 1%.