| 摘要 |
PURPOSE:To secure switching of a power converter in the shortest period of time for current being kept zero by switching upon detecting a voltage having been impressed on a positive side arm and a negative side arm of the other bridge after interrupting gate pulse of one thyristor bridge. CONSTITUTION:When switching from a thyristor bridge 3A to 3B, an output current of the bridge 3A decreases in accordance as a current command value decreases, and when the current command value becomes negative, a current direction command signal 8 changes. When output current of the bridge 3A becomes zero, an output of a microcurrent detection circuit 7 changes, FF10 is reset, and an ignition pulse of the bridge 3A is interrupted. A back pressure is applied on an element of the bridge 3A, and when arm voltage detection circuits 11-16 detect a voltage being applied on a negative side arm of bridge 3B, the bridge 3B is ignited to switching from positive side to negative side. A time whereat an arm voltage of the thyristor rises can be detected, therefore switching can be secured in the shortest period of time for current being kept zero by detecting an instant for the thyristor to come off. |
