Wide bandwidth, large AC current probe for power electronics and EMI measurements

Current measurements in power electronics or in EMI domains require high-performance probes. These probes must have a very wide bandwidth, be insensitive to electromagnetic interferences, and be able to measure large direct and alternating currents (AC-DC) without distortion. This paper is limited to AC current probes. Various principles are reviewed, in particular those based on the current transformer (CT); their limitations are analyzed, and a solution based on a two-stage transformer are proposed to extend low- and high-frequency performance. It is shown that the use of new magnetic materials, such as the amorphous or the nanocrystalline, can improve large-current low-frequency operations, while preserving the smallest possible probe size. Various solutions are provided to improve high-frequency operations. Different developments are depleted; frequency and time-domain results are presented.