An Improved Calculational Model for Inductance of CRDM Based on Equivalent Magnetic Circuit

In the magnetic lifting control rod drive mechanism (CRDM), it is essential to obtain the dynamic inductance of each coil for research of a mathematical model and state monitoring. It is demonstrated from the working principle and circuit model of the CRDM that the coil inductance has a significant effect on the current step response time. This article proposes an improved equivalent magnetic circuit (IEMC) model that takes into account flux leakage and coupling. The model focuses on calculating the dynamic inductance of the CRDM. First, the magnetic reluctance expression of each unit in the IEMC model is deduced. A flux area correction coefficient is introduced to consider the edge effect of working air gaps. Then, the dynamic inductance of the CRDM is analyzed and calculated based on the proposed model. Finally, the performance of the proposed method is compared with finite element analysis (FEA) and a simplified equivalent magnetic circuit (SEMC) method. Results show that the proposed method can approach the results of FEA better than the SEMC method.