| 摘要 |
PURPOSE: To prevent the erroneous function of overvoltage protection circuit by the overshoot of output voltage from an active filter by increasing the overvoltage decision level in an overvoltage prevention means for active filter for a predetermined period at the time of starting the active filter or a motor compressor. CONSTITUTION: An overvoltage protection circuit at a switching control section 7 for controlling a power transistor 33 in an active filter 5 connected between a bridge rectifier 2 and a smoothing capacitor 5 comprises a comparator 54 for comparing the output voltage from the active filter 5, divided by resistors 56, 57, with an overvoltage decision level, divided by resistors 51, 52. A switch 55 is closed by a command from an inverter control section 8 for a predetermined time after starting the active filter 5 or a motor compressor 6 to connect the resistor 53 with the resistor 51 thus elevating the protection voltage. This circuitry prevents by erroneous function of overvoltage protection circuit owing to overshoot of output voltage from the active filter 5. |
