| 摘要 |
PURPOSE:To minimize the change of air flow amount by a method wherein the output of a variable frequency electric source (V electric source) is increased to a predetermined value when the abnormality of frequency commanding signal is detected in the air flow amount control device to switch the electric source into commercial electric source. CONSTITUTION:When the abnormal frequency commanding signal is detected by a detecting unit 9, the output frequency of the V electric source is increased to the upper limit thereof at a predetermined increasing rate, thereafter, the electric source is switched into the commercial electric source 1. According to this method, the rotating number of a motor 4 is increased suddenly after it is reduced and an inlet vane is operated in accordance with the sudden increase, therefore, the transitional fluctuation in the air flow amount may be minimized and the device may be operated in safe continuously.
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