| 摘要 |
<p>PURPOSE:To improve the performance of a magnetic shield, to enhance balance characteristics and to prevent a malfunction by setting magnetic flux density in the magnetic shield to the magnitude or less of the saturation magnetization of a magnetic shielding material. CONSTITUTION:The thickness of magnetic shielding materials 8, 9, 10 covering the inner circumference, outer circumference and side face of an annular core 2 is set in thickness, in which magnetic flux density in a magnetic shield is set to the saturation magnetization or less of the magnetic shielding materials. The thickness of the magnetic shielding material 8 arranged inside the annular core 2 is shown in formula I when a primary conductor consists of three phase and in formula II when the primary conductor is composed of single phase. Where mu0 represents the permeability (4XPIX10<-7>(H/m)) of a vacuum, In the execution value (A) of the balance currents of the primary conductor, K the compression of the annular core and M the magnitude (T) of the saturation magnetization of the magnetic shielding material. Accordingly, magnetic flux manufactured by the primary conductor at the time of three-phase balance is interrupted sufficiently by the magnetic shield, and the output voltage of a secondary winding can be lowered, thus preventing a malfunction.</p> |
