| 摘要 |
PURPOSE:To prevent a superheating burnout of a motor through electrical constraint by detecting a terminal voltage of a bidirectional thyristor and keeping a gate signal of another bidirectional thyristor in an unignited state when the detected terminal voltage is in an ON state. CONSTITUTION:Zero-crossing circuits 35, 45 and energy-saving circuits 36, 46 give a synchronous signal of gate current to gate input amplifier circuits 6A, 7A, only if a terminal voltage of bidirectional thyristors 3, 4 is larger than the maximum value of an ON-state terminal voltage of said bidirectional thyristors, when these thyristors are turned ON, and smaller than an ignition upper limit voltage. At the same time, they give a current blocking signal to gate input amplifier circuits 7A, 6A of another bidirectional thyristor for the circuit direction via simultaneous ON prevention circuits 37, 47. In this manner, it is possible to prevent bidirectional thyristors from being turned ON simultaneously and a motor from being superheated and burnt out. |
