| 摘要 |
PURPOSE:To electrically make movable the position in which an AC magnetic flux is generated by a method wherein multiphase AC wiring capable of causing excitation over the magnetic saturation point is provided on the plural number of iron cores to allow a shifting magnetic field to occur in the direction of the row of the magnetic poles of the cores. CONSTITUTION:A material 6 under inspection is moved in an arrow direction 7, while its end parts are detected by photoelectric detectors 8, 8'. Signals from the detectors are used as ones for permitting a space counter 9 to start counting. The rotation of a table roll 10 is detected by a pulse generator 11, while a signal from the pulse generator is entered to the space counter 9, so that the length of a material 6 under inspection is measured by the photoelectric detectors 8, 8'. A magnetic head 13 consists of multiphase, for instance, 3-phase AC wirings 5u-5w wound on iron cores 4a-4j and a flaw detecting coil, that is, signal wiring 14. When 3-phase AC current is sent to the 3-phase AC wirings 5u-5w, a shifting magnetic field is generated, and the iron cores 4a-4j periodically repeat magnetically saturated and unsaturated conditions because of shifting magnetomotive force. The signal from the signal wiring 14 is sent to a display unit 17 from a controller 12. |
