| 摘要 |
PURPOSE:To detect, with satisfactory S/N ratio, breakage of strand while being used as an overhead stranded wire, by employing two coils of the same specification, such as rectangular and annular coils whose generating magnetic field distributes uniformly to a relatively long range in a particular direction. CONSTITUTION:This is to consist of rectangular coils 1 and 2 each of which is annular and has a side longer than outside diameter of an object to be detected, and these coils 1 and 2 are of the same specification and are arranged in such positions that their respective sides being longer than the work 3 become parallel with each other. It is also necessary to give such a consideration to arrangement of the coils that the sides being longer than the work 3 are to become perpendicular to axial direction of the work 3 and axes of the coils 1 and 2 become to face a flaw-seeking face 3a of the work 3. As distribution of the eddy current to be induced to the work 3 passes annularly in the neighborhood of the flaw-searching face 3a, influence by contact resistance between strands can be minimized. On the other hand, if location of breakage of strand falls immediate under axis of a coil, the eddy current becomes largely disturbed and impedance of the coil changes remarkably. And therefore, it is possible, by using this mechanism, to detect, with satisfactory S/N ratio, breakage of strand while being used as an overhead stranded wire. |
