| 摘要 |
PURPOSE:To improve an impulse resistance and safety and long-life reliability by a method wherein two vacuum bulbs are connected in series between a movable contact of a tap selector and a draw-out terminal of a change-over switch and a current limiting resistance and a non-linear resistance are connected in parallel to the vacuum bulb located near the draw-out terminal of the change-over switch. CONSTITUTION:A vacuum bulb V2 is connected in parallel to a current limiting resistance R1 and a non-linear resistance NR1 and a vacuum bulb V1 is connected in series between a movable contact 2 of a tap selector and the parallel circuit composed of the vacuum bulb V2, the current limiting resistance R1 and a non-linear resistance NR1 and the side, which is not connected to the vacuum bulb V1, of the parallel circuit composed of the vacuum bulb V2, the current limiting resistance R1 and the non-linear resistance NR1 is connected to a draw-out terminal 4. When a current is applied to the circuit of the side of the movable contact 3 of the tap selector, the vacuum bulb V2, the current limiting resistance R1, the non-linear resistance NR1, connecting conductors 6, 7 and one of the contacts, which is connected to the conductors 6, 7, of the vacuum bulb V1 have the same potential as the circuit to which the current is applied. Therefore, no voltage is applied to the non-linear resistance NR1 and the long-life reliability of the non-linear resistance is improved. |
