| 摘要 |
PURPOSE:To protect a reactor and a thyristor from being overloaded by employing a control method which permits a temporary overcurrent to flow temporarily on condition that a time for constant-time cooling is secured after the temporary overcurrent is made to flow through the reactor and thyristor for overvoltage suppression. CONSTITUTION:When an overvoltage is generated at a point tA, the output of an overvoltage detecting circuit 10 varies from 0 to 1 and the output of a timer 11 varies from 0 to 1 accordingly and continues in the state for a constant time t1. Simultaneously, a switch 12 couples an alphaT limiter 8-2 with a pulse amplifier 9 and SVC flows the overcurrent for the overvoltage suppression. Then, the timer 11-1 varies from 1 to 0 a period t1 later, the switch 12 couples an alphaC limiter 8-1 with the pulse amplifier 9, and the output of a timer 11-2 varies from 0 to 1. The SVC, therefore, flows a current limited by a continuous maximum current limit alphaC. Then, control is so carried out that the overcurrent is flowed a constant time T2 later. |
