| 摘要 |
PURPOSE:To detect abnormal operation, such as minimum flow or the like, inexpensively with a good accuracy, by a method wherein the operating condition of a rotary load machine, such as a pump, a blower or the like, is detected by the input power of a motor and the frequency of the same. CONSTITUTION:A control unit 11 is constituted of a memory unit, storing a corresponding relation between the input power and the frequency of a motor 4a with respect to the limit of minimum flow, and a comparing unit, comparing the measured values of power measuring units 9, 9' and a frequency measuring unit 10 with the corresponding relations. According to this constitution, the operating condition of a pump 1a is detected whether normal operation is being effected without exceeding the limit of minimum flow or not. An invertor 3 is controlled by such detecting signals whereby the delivery flow rate of the pump 1a may be held higher than the minimum flow. |
