| 摘要 |
In a PWM voltage type inverter system comprising: a rectifier converting an AC power from an AC power source into a DC power, an inverter bridge converting the DC power from the rectifier into an AC power of a variable frequency to supply it to an AC motor, and a conduction control circuit for controlling the conduction of arms of the inverter bridge normally in a first mode wherein it operates at a frequency determined by a frequency reference signal, a control power circuit is connected to receive the power from the AC power source and the regenerative AC power from the motor and to supply a constant voltage DC power to the conduction control circuit. When power failure is detected, the conduction control circuit is switched to a second mode, wherein it operates in such a manner as to maintain the regenerative voltage at a predetermined value. With the arrangement of the invention, the motor can be kept operating over a longer period of time upon occurrence of power failure.
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