C-Shape Busbar With Frequency Invariant Points for Wideband Current Measurement

A yokeless busbar current transducer with frequency-invariant points is presented for the first time in this article. Existing rectangular busbar current transducers suffer from the frequency dependency issue due to the eddy currents in the massive busbar. The proposed transducer has a novel C-shaped structure for the sensing area of the busbar. It is observed for the first time that this structure provides sets of frequency-invariant points on both sides of the C- shaped busbar. In the proposed scheme, two integrated fluxgate sensors in differential form are used to measure the magnetic flux densities at those invariant points. A finite-element method (FEM)-based three-dimensional analysis performed using the Ansys Maxwell eddy current solver provided the exact locations of the frequency-invariant points. A prototype was made, and functionality tests of the C-shape busbar transducer have been carried out in the laboratory using DRV-425 integrated fluxgate sensors from Texas Instruments. In the experiment, fluxgate sensors placed at frequency-invariant points measured the flux densities at multiple frequencies varying from 50 to 4000 Hz. The results obtained from the tests showed that the error due to frequency dependency has been reduced from 14% to −0.85% using the proposed C-shape busbar.