| 摘要 |
PURPOSE:To enable the AC demagnetization of thick steel plates of 30mm. thick or more by a method wherein demagnetizing frequency of an AC flowing in a demagnetizing coil is converted by a frequency converter according to the thickness of the steel plate so as to maintain demagnetizing power by supplementing a decline of it caused by the skin effect. CONSTITUTION:When residual magnetism of a steel plate 1 is demagnetized, induced voltage and operating time of an induced voltage adjuster 3 are controlled and alternating current generated by a transformer 4 is flowed into a demagnetizing coil 2, thereby driving the residual magnetism of the steel plate 1 into a direction of zero so as to attain magnetization. Nextly, in case of a thick steel plate of 30mm. thick or more, a frequency of the AC (a demagnetizing current) generated by the transformer 4 is decreased by a frequency converter 5 so that it might have the wave form close to that of a direct current. Consequently, as the magnetizing time becomes longer, the residual magnetism even of the central portion of the thick steel plate can be AC-demagnetized. |
