| 摘要 |
PURPOSE:To increase the energizing lifetime of a ground installation coil by constructing a coil conductor, an inner sheath, and an outer sheath of a combination of materials having smaller thermal expansion coefficients in the sequence of the conductor, the outer sheath and the inner sheath, thereby eliminating gaps thereamong. CONSTITUTION:An inner sheath 4 made of an insulator is coated on a coil conductor 1, and an outer sheath 3 made of other insulator different from the insulator of the sheath 4 is provided outside the sheath 4. Here, the conductor 1, the sheaths 4, 3 are selected for the materials having smaller thermal expansion coefficients in the sequence of the conductor 1, the sheaths 3, and 4. |
