Novel Broadband Calibration Method of Current Shunts Based on VNA

Abstract

Usually high wideband ac current and harmonics measurements are accurately achieved in industry and laboratories by using high accuracy shunts or standard shunts. For particular applications, such as power and transient measurements, it is mandatory to evaluate the shunt impedance phase and magnitude according to the frequency bandwidth of interest before to measure the current with such sensors. High electrical current shunt beyond 1 A is calibrated in magnitude up to 100 kHz and in phase angle up to 200 kHz only by a few National Metrology Institutes. The existing traceable measurement methods to characterize these sensors are limited in frequency to 100 kHz, with expanded uncertainties of the ac–dc difference (magnitude) and the phase angle of more than $5 \times 10^{-6}$ and $62~\mu $ rad at 100 kHz, respectively. A new traceable calibration method to measure and characterize current shunts at high frequencies is presented in this paper. This measurement method is based on the use of a vector network analyzer. The measurements are presented up to 60 MHz, but theoretically, the presented method does not exhibit a specific frequency limitation. Only the characteristics of the shunt under study can impose limitation in practice. While uncertainties are higher than those provided by the existing methods, the method presented in this paper is the only method able to perform in one step a broadband and simultaneous measurement of the magnitude and phase of current shunts up to few megahertz with acceptable uncertainties.