Abstract：The equivalent model of four-terminal ac shunt was introduced. An ac impedance bridge using the zero flux current transformer(ZCT) as the current proportional standard was constructed to measure the main parameter of the ac shunt. A multi-decade two-stage inductive voltage divider was used to divide the voltage of the standard ac resistor. The differential measurement circuit was used to measure the voltage difference between the shunt under test and the standard ac resistance. The bridge signals were sampled by the dual-channel synchronous sampling system and the voltage amplitude ratio and phase difference were calculated by the discrete Fourier transform algorithm. Then the resistance and time constant of the ac shunt can be computed. Verification experiments showed that the measuring device can achieve precise measurement of ac shunts below 100A in the frequency range of 20Hz~3kHz. The optimum expanded uncertainty of time constant is 8 ns.
2025, Vol. 46 
