Current measurement using compensated coaxial shunts

A novel approach to the construction and compensation of a coaxial resistive shunt is shown to produce significant improvements in performance when compared with equivalent shunts employing a conventional method of construction. A full theoretical treatment shows how the adopted measurement and compensation scheme provides a simple and realisable method for the elimination of skin effect errors in thin-walled shunts. These findings are employed in the design and construction of a current measurement system, rated at 5000 A with a 20 ns risetime, for use in a power semiconductor test rig. Experimental results concentrate on a comparison of the new shunt with an equivalent, conventional coaxial shunt and clearly demonstrate the improvements possible. The usable risetime and bandwidth are shown to be improved by an order of magnitude with excellent phase characteristics and a significant reduction in susceptibility to conducted and radiated interference