FEM simulations in designing saturated iron core superconducting fault current limiters

Proper design of the iron cores is crucial for a saturated iron core superconducting fault current limiter. An optimized design requires guaranteeing sufficient magnetic saturation on the iron cores holding the ac coils, ensuring the efficiency of current limiting, minimizing the use of materials, as well as satisfying the safety and stability obligations. One of the key tasks in the design is the series of electromagnetic calculations, including the complex three-dimensional electromagnetic field calculation. It is extremely difficult to calculate the magnetic field distribution through purely analytical methods because of the nonlinearity of magnetization for a ferromagnetic material. We used Finite Element Method (FEM) to solve the field distribution problem, and adopted Ansoft Maxwell for the computer simulation. Simulation results revealed that the iron cores with varying cross-sections of different windows were most effective for obtaining ideal magnetizing force distribution. Optimized design of the iron cores could be based on this simulation method. Experiments on a 380V/30A prototype were carried out to verify the designs.