| 摘要 |
PURPOSE:To stably operate an inverter without stalling a motor by reducing the frequency of the inverter in the prescribed frequency when the current of the motor increases and becomes the state exceeding a stalling preventing level. CONSTITUTION:Since the current I0 of a motor 4 for detecting through a current detector 7 and a current transformer 6 is lower than a stalling preventing level at normal time, a level discriminator 8 does not energize a signal 8a. Thus, an inverter controller 9 inputs a control signal 9a to an inverter 3. Here, when the slip frequency fs of the motor 4 increases due to certain cause and the current I0 exceeds the stalling preventing level, the discriminator 8 energizes the signal 8a. Accordingly, the value of the output frequency command is abruptly reduced in response to the signal 9a of the controller 9. Thus, the slip of the motor 4 increases to prevent the motor from stalling. |
