| 摘要 |
PROBLEM TO BE SOLVED: To stop voltage supplied to a smoothing capacitor and to prevent its destruction by allowing a microcomputer to control an electromagnetic relay drive circuit, which opens and closes main power supply and to forcibly turn off an electromagnetic relay at the time a decision circuit of an AC input voltage decides an abnormal rise through a remotely controlled transformer. SOLUTION: The secondary side voltage of a remotely controlled transformer 1 also fluctuates according to the fluctuations of an AC input voltage, and this voltage is inputted to a decision circuit 10 of an AC input voltage through a rectifying smoothing circuit 2. Reference voltage is set to the decision circuit 10, and when it is discriminated that an AC voltage exceeding the reference voltage is inputted, it controls to turn a switch circuit 11 off. Then, a microcomputer 4 releases a control line of main power supply to an electromagnetic relay drive circuit 5, forcibly turns an electromagnetic relay 6 off and stops the supplied voltage to a smoothing capacitor 8. Thus, it prevents the smoothing capacitor 8 from being destroyed at abnormal rising of AC input voltage. |
