Recently, color change and distortion in CRT television sets due to residual magnetization in steel structure of building has been troublesome in offices, hospitals, and houses. The residual magnetization is caused by welding current and lifting magnet. In order to investigate an effective method of removing the residual magnetization by a demagnetizing coil, a method of evaluating magnetized and demagnetized areas in the steel structure by means of the 3-D nonlinear magnetic field analysis using the finite element method was proposed. The tendency of the magnetic fields obtained from the proposed method was in good agreement with the experiment. Moreover, the optimal setting of a square demagnetizing coil was also discussed. It was found that the setting of the demagnetizing square coil perpendicular to the floor is more effective than that parallel to the floor from the standpoint of demagnetized area.
