Variable inductors, which are composed of only a magnetic core and primary dc and secondary ac windings, can control the effective inductance of the secondary ac winding linearly and continuously by the primary dc current due to the effect of magnetic saturation. Variable inductors have advantageous features such as having a simple, and robust structure, and high reliability. Therefore, they can be applied as var compensators in electric power systems. A 6-leg three-phase laminated-core variable inductor was proposed in a previous paper. It had only one laminated-core in which three-phase secondary ac windings were installed, to reduce its size and weight in comparison with conventional single-phase variable inductors. A 18-leg three-phase-laminated-core variable inductor is proposed in this paper to further reduce size and weight. The basic characteristics of the proposed variable inductor were calculated based on reluctance network analysis (RNA).
