Patent ID: 8608450
Filing Date: 2013-12-17
Classification: F04B

Abstract:
1. A compressed air manufacturing facility comprising: a plurality of compressors compressing air; a plurality of electric motors respectively driving said plurality of compressors; and a control apparatus operating a first compressor corresponding to one of said plurality of compressors by variously controlling a rotating speed of said electric motor corresponding thereto via an inverter, and switching a second compressor of said plurality of compressors to a full-load operation state of operating by setting the rotating speed of said electric motor corresponding thereto to an upper limit value or a stop state, said control apparatus computing a pressure loss of a discharge air system connected to a discharge side of said first and second compressors in correspondence to the rotating speed of said electric motor corresponding to said first compressor and the rotating speed of said electric motor corresponding to said second compressor, and changing a control range of a discharge pressure of said first compressor at an upstream side position of said discharge air system on the basis of the computation in such a manner that a terminal pressure at a downstream side position of said discharge air system comes to a predetermined range; said control apparatus variably controlling the rotating speed of said electric motor corresponding to said first compressor via said inverter in such a manner that the discharge pressure of said first compressor detected by a pressure detecting means comes to the control range changed by said control apparatus; and said pressure detecting means detecting the discharge pressure of said first compressor at the upstream side position of said discharge air system; wherein said control apparatus changes an unload start pressure in such a manner that the terminal pressure of the discharge air system comes to a predetermined range, on the basis of the computed pressure loss of the discharge air system, and controls in such a manner as to switch the first compressor to an unload operation in the case that the discharge pressure of the first compressor detected by the pressure detecting means at a time of the load operation of the first compressor is increased up to the unload start pressure, and the unload start pressure is different between the load operation time of the second compressor and the stop time thereof.