C-SHAPED COIL

PROBLEM TO BE SOLVED: To provide a C-shaped coil which can be operated without anxiety over a long time, by interposing insulation paper between adjacent electromagnetic steel plates to avoid overheating of an iron core. SOLUTION: A C-shaped coil is constituted of plurally superposed electromagnetic steel plates 3 of C-shaped iron core 4, side plate 10 of fastening water-cooled copper plates 6 and the iron core and through bolts 7. However, in the upper/lower iron cores 4 of an air gap 2, a pitch of the copper plate 6 is formed small as compared with in the center part. In a part of the upper/lower iron cores 4 of the air gap 2, a water-cooled copper-made coil 5 is wound, to generate magnetic flux inside the iron core and in a magnetic path of the air gap. A high frequency current is allowed to flow in the coil 5, to supply also cooling water 8. Insulation paper 11 is interposed between the electromagnetic steel plates 3 and also between the steel plate 3 and the water-cooled copper plate 6. Further the dimension of the steel plate 3 is made smaller than a water-cooled pipe 6 in the outside, to be made in the dimension of the center part electromagnetic steel plate 3 via stages. Thickness of the side plate 10 or of the water-cooled copper plate 6 near the side plate is formed larger than the thickness of the copper plate 6 near the center in accordance with a heating frequency.