Wide Bandwidth Rogowski Current Transducers:

Abstract

SummaryThis paper is the second of three parts giving a comprehensive examination of the use of Rogowski coils for wide bandwidth current waveform measurement. Rogowski coils have previously been used for special applications of current measurement such as very short duration high current pulses, but have only recently become available as general purpose transducers suitable for power electronic equipment. This requires a bandwidth of 50 Hz to at least 1 MHz for performance comparable to a standard co-axial shunt. Part I examined the Rogowski coil design and behaviour. Part II examines the integrator behaviour at both low (50 Hz) and high (1 MHz) frequencies. It introduces a feedback circuit which overcomes the problems of low frequency noise and drift and it also shows that with appropriate choice of operational amplifier the bandwidth can be extended beyond 1 MHz. Theoretical noise content is quantified and a transfer function model of the complete transducer is developed. Part III provides results of frequency response tests and recordings of current waveforms with dI/dt up to 3500 A/µs for different coil designs and alternative operational amplifiers.