| 摘要 |
An object of the present invention is to make it possible, without interfering with the operating region of a motor, to more strictly judge inverter operation that deviates from the operating region in a low rotating speed area, so as to carefully protect the inverter. Two current threshold values I TH1 and I TH2 are adopted, which are larger than the upper limit I U of current of an operating region D. When a rotating speed Rot is smaller than a speed threshold value RTH1, the current threshold value I TH1 is adopted as a criterion to judge whether an input current i INV to an inverter is abnormal, and when the rotating speed Rot is larger than that, the current threshold value I TH2 is adopted as the criterion. |
