| 摘要 |
PURPOSE:To prevent a trouble such as overhead or burnout of a motor by stopping the phase control to interrupt a motor current when the pause time of supplying current to a motor armature becomes shorter than the predetermined time. CONSTITUTION:When switches SW1, SW2 are operated, a voltage VD is outputted in response to a speed command, and a capacitor C2 repeatedly charges and discharges due to the voltage Vd in synchronization with a power source period. A capacitor C3 is charged by the speed electromotive force when a transistor Tr6 is interrupted during the period while the armature current becomes 0. When a voltage VE becomes higher than a voltage V1, a PUT2 is conducted, thereby applying a firing angle to thyristors SCR1, SCR2. On the other hand, a capacitor C4 is charged when a transistor Tr7 is interrupted during the period while the armature current becomes 0. When the voltage VD becomes higher than a voltage VK, the PUT1 is conducted, thereby interrupting the current of a motor M. |
