| 摘要 |
PURPOSE:To enable a semiconductor AC switch to be of the rated nature for short time and to reduce the capacity thereof by a method wherein contact, which by-passes the semiconductor AC switch, is provided and a contact switch is subjected to taking a share in load current at stationary time, then ON-drive is performed to the semiconductor AC switch for very short time covering forward and backward ON-OFF timing of the conduct switch. CONSTITUTION:When tap switching is performed, potential difference Us between potential of the primary voltage tap 2 and the secondary voltage tap 3 is impressed to a nonlinear resistance element 9. However, since discharge voltage has been lager than instantanious max. voltage of voltage difference between both voltage taps, bridge current by potential difference is not sent through the nonlinear element 9 and still load current IL is output through a tap winding 1 to the primary voltage tap 2 to the primary moving contact piece 4 to a contact switch 10. After minute time, a thyrister switch 6 is subjected to ON-drive, but almost the load current IL is sent through the tap winding 1 to the primary voltage tap 2 to the primary moving contact piece 4 to the conduct switch 10 since forward voltage drop of the thyrister switch 6 is small. |
