| 摘要 |
<p>A magnetic flux density B which is 0.75-0.9 times as dense as that of the axial magnetic flux density (Bcr) at which the arc voltage between electrodes becomes the minimum with respect to each breaking current is impressed upon the center of an electrode and the axial magnetic flux density is monotonously increased from the center toward the periphery of the electrode. The radial position upon which the axial magnetic flux density (Bcr) at which the arc voltage becomes the minimum Vmin is in the range of 20-40 % of the radius of the electrode. The axial magnetic flux density is further increased from this range monotonously toward the outside so that the density becomes the maximum (Bp) outside the 70 % radius of the electrode. The maximum value (Bp) is 1.4-2.4 times as dense that of the magnetic flux density (Bct) at the center of the electrode. The distribution of the axial magnetic flux density in the circumferential direction of the electrode at a radial position in the peripheral area of the electrode at which the axial magnetic flux density becomes the maximum is changed unevenly. The axial direction magnetic flux density in the circumferential direction is distributed so that at least two peaks appear over the full circumference. The maximum value (Bmax) and minimum value (Bmin) of the circumferential magnetic flux density distribution are 1.4-2.4 times as dense as that of the axial magnetic flux density (Bct) at the central part of the electrode.</p> |
