| 摘要 |
<p>PURPOSE:To enable switching time to be reduced and productivity to be improved by allowing one of primary coils for high frequency and medium frequency according to a frequency to be used to be rapidly moved to be engaged to a secondary coil when heating a work at a different frequency in a welding line. CONSTITUTION:When welding an electric seam welded steel pipe by supplying a medium-frequency power to a work coil 30, an oscillation frequency of a power supply main unit 26 is switched to a specified medium frequency. A primary coil for high frequency 21a operates a ascending/descending mechanism 20 from a state where the primary coil for high frequency 21a is engaged to a secondary coil 23, lowers a primary coil 21b along with a supporting frame 22, and then places the primary coil for medium frequency 21b at a position which is engaged to the secondary coil 23. A switcher 25 is operated and the power supply main unit 26 and the primary coil for medium frequency 21b are connected. A cooling water is supplied to the primary coil 21b through a rotary joint 31.</p> |
