| 摘要 |
PURPOSE:To prevent the fan from rushing into surging condition surely and improve reliability by a method wherein the operating condition of the fan is detected that it has exceeded an alarm area corresponding to the limit of surging and the load of the fan is run back quickly by the detecting signal. CONSTITUTION:When the fan has rushed into the limit of surging, an auxiliary relay X1 33 is operated through a timer relay T1 32 and the load of the fan is run back to a proper load by the contact of the relay X1 33 to protect the fan through a sequence circuit shown in the diagram. Further, in addition to the detection through said time limit, the draft of a furnace upon rushing into the surging alarm area is detected by a detector 34 to detect that the draft is larger than the specified draft of a boiler or the vibration of the fan is detected by the detector 35 that the value of vibration is higher than a specified value. Then, the auxiliary relay X2 37 is operated by the time relay T2 36 through a malfunction timer to run back the fan through the contact of the relay X2 37. According to this method, inrush of the fan into the surging condition may be precluded surely and the reliability of the fan may be improved.
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