| 摘要 |
PURPOSE:To prevent stalling even under overload by automatically varying a stall prevention level in accordance with a frequency. CONSTITUTION:The load current of an induction motor 5 is detected by a current transformer 6 and compared with a stall prevention level from a stall prevention level command circuit 10 by a comparator 9. When current gets larger than the stall prevention level, the output frequency of an inverter 4 is decreased or fixed. Here, a stall prevention command circuit 11 always monitors the output frequency of a frequency command circuit 7. When the output frequency of the inverter 4 exceeds the rated frequency of the induction motor 5, the stall prevention level is automatically varied in accordance with the frequency. |
