| 摘要 |
PROBLEM TO BE SOLVED: To prevent an element destruction phenomenon at the time of small current by discriminating whether or not a setting value to a current setter is a set lower-limit current value or less and, if so, shifting the phase angle of gate trigger pulse to such a maximum angle that rectifying output becomes zero. SOLUTION: When current lower setting operation is performed with a current setter (S101), a current controller delays the operation of a rectifier, following its setting value, so that real current is decreased (S102). This operation is repeated until the real current reaches a current value A [kA] which causes current interruption at the time of small current. When the real current is A [kA] or less (S103 Yes), the control angle of a thyristor is shifted untilαmax which causes the real current to become zero is reached. In stopping the operation in this way, the output current of the rectifier 2 become zero immediately from A [kA]. Therefore, the operation is stopped without experience of the operating state of small current, thereby eliminating an interruption phenomenon.
|
