| 摘要 |
PURPOSE:To prevent a commutation failure occurring by a voltage distortion generated through switching in a capacitor by making a phase-control angle betalarge to the limit of the allowable heat capacity of a snubber circuit to operate the title system through equipping a means for determining the maximum determination time during which a thyristor valve can be operated for a specified phase-control angle beta. CONSTITUTION:An information processing equipment 12 outputs the values of the cooling water temperature T of a thyristor valve, AC bus voltage V and phase-control angle beta from a controller to a determination circuit 13. The determination circuit 13 stores beforehand characteristics of the heat tolerance of a thyristor valve indicating the relation between the phase-control angle betaand allowable operating time (t) by using the AC bus voltage and cooling water temperature as parameters. Therefore, the allowable operating time (t) at that point of time is determined in an instant by information from the information processing equipment 12 and sent to converters 3, 3'. After the converters 3, 3' start operation by the phase-control angle beta from the controller, they stop the operation by the phase-control angle beta after the time (t) and return to the operation by a small phase-control angle beta. |
