The magnetization state of a magnetic core can be adjusted and controlled by a dc bias coil. A significant voltage may be induced on the bias coil if the coil is coupled with a coil carrying alternative current through the magnetic core. In some practical applications, this induced voltage can cause significant problems. We designed a new type of orthogonally configured core structure to reduce or eliminate the induced voltage. In this design, a C-shape iron-core was orthogonally assembled with a closed iron-core. The closed iron-core was set through the gap of the C-shape core. The C-shape iron-core was wound with the working coil carrying alternative current, while the closed iron-core was with the dc bias coil. Under this configuration, the impedance of working coil could be controlled by applying different dc currents to the bias coil without the risk of inducing voltage on the coil. In our studies, computer simulations as well as laboratory experiments were conducted under different conditions. Test results show that the adjustable impedance range of the working coil is 27%. One of the potential applications for this technique is superconducting controllable reactor for power grids. In this paper, we will present the details of this study.