| 摘要 |
PURPOSE:To enable to minimize the total suction/exhaust air flow by a method wherein the rotational frequency of suction/exhaust fan is controlled so as to make the suction/exhaust air flow constant by coinciding the operating air flow of the fan with the total set air flow. CONSTITUTION:Measured exhaust air flow QT is calculated based upon an inputted air velocity signal V (not shown) and a predetermined sectional area of a concentrated duct 4. Next, the difference between the total set air flow QE (not shown) and the measured exhaust air flow QT is calculated. A control signal for rotational frequency of an exhaust fan 5 is determined so as to bring said difference to naught or to make QT equal to QE (not shown) and then outputted to the fan control device 5a of the exhaust fan 5. In such a manner as described above, even if the number of individual suction/exhaust units in operaion may change, the air flow of each unit can be kept at the set value and at the same time the total exhaust air flow can be controlled to the minimum by making the total exhaust air flow equal to the total sum of air flow of each unit. |
