| 摘要 |
PURPOSE: To protect the circuitry by providing a protective circuit for preventing voltage rise when the voltage being supplied to an inverter exceeds a reference level thereby detecting an overvoltage. CONSTITUTION: Overvoltage is detected by connecting a DC circuit of a diode 11 and a capacitor 12 for ensuring a current path at the time of starting a converter 2 to the output side thereof, for example, and connecting a discharge circuit, i.e., a voltage division resistor circuit 13, in parallel with the capacitor 12 and then detecting the divided voltage by means of a voltage detector 14. When an overvoltage is detected by means of the voltage detector 14 and an overvoltage decision circuit 13, a protective circuit 8a takes countermeasures against overvoltage, e.g. lowering of the target level of constant current control or short circuit of an inverter 6, thus protecting a machine against overvoltage. Furthermore, the overvoltage protector can be made compact while ensuring reliable starting of the converter 2 by utilizing the circuit, provided for ensuring a current path at the time of starting the converter, partially as a voltage division circuit when the overvoltage is detected. |
