| 摘要 |
PURPOSE:To elevate a heating efficiency without eddycurrent loss by providing the coil winding a work coil so that the flowing direction of the current is made same on the inner side of an open pipe and tube and by feeding thereto the current that the current value and phase are adjusted. CONSTITUTION:The current Ic', Ib' in the same direction with both sides edge part Ia and in the reverse direction with Ia is flowed on the pipe outer face and inner face respectively, when the current value and phase are set adequately and the current is flowed on a coil 5. The induced current to pass the inner face side of open pipe 1 and tube 4 to be generated by a work coil 2 can be thus made smaller. Consequently a welding current Iw' can be made larger. With the above the induced current which does not contribute to the welding of the inner face of the open pipe 1 is controlled and the eddycurrent loss is reduced.
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