| 摘要 |
PURPOSE:To prevent magnetic deflection by detecting a magnetic deflection current to correct firing angles given to forward and reverse thyristors. CONSTITUTION:A current signal IR detected by a current transformer CT is converted to a voltage value, and track holding is performed by a track holding circuit 15 if either of a forward voltage signal FVu and a reverse voltage signal FVx is '1'. The output value of the track holding circuit 15 is multiplied by a coefficient K2 in a coefficient device 16 to determine a firing angle deviation signal DELTAalpha. This signal DELTAalpha is used as the correction value for firing angles alphau and alphax of forward and reverse thyristors, and currents of forward and reverse thyristors are so adjusted that DC deviation components of positive and negative currents are cancelled, thus reducing the DC deviation component of the current. |
