Analysis of the Open-loop Linear Range and Construction of the Small-signal Model of DCCT Applied to the FTPMF System

The accuracy of current measurement directly determines stability of the high flat-top pulsed magnetic field (FTPMF), which is a key aspect in some scientific studies. The Direct-Current Current Transformers (DCCT) is the best choice to achieve the high accuracy of current measurement. Different from the conventional DC current measurement, the DCCT is prone to be unstable in the FTPMF system due to the nonlinearity of the open-loop characteristic of DCCT. In this paper, the cause of nonlinearity of the open-loop characteristic is analyzed in detail, and a formulation is obtained to estimate the open-loop linear range (OLR). The relationship between the response time and OLR is proposed to make the DCCT stable. Then, a small-signal model is established to optimize the control parameters of the DCCT and a prototype of 30 kA is developed.