| 摘要 |
It is an object of the present invention to make it possible to control a discharge pressure in a multi-stage variable speed compressor always to be a desired target pressure, whereby the multi-stage variable speed compressor can be operated with a discharge pressure of a good precision and to make it possible to perform the control without needing operation data as used in the prior art, at all. For all of the compressors constituting the multi-stage variable speed compressor, the rotational speed of each compressor is determined based on a deviation of the discharge pressure from the desired target pressure. Herein, the relationship between the rotational speeds of compressors of respective stages is previously set. The multi-stage variable speed compressor further comprises a pressure detector provided for each compressor on and after the second stage among said plurality of compressors for detecting a discharge pressure of a compressor of a stage preceding the corresponding compressor or a suction pressure of the corresponding compressor, wherein said control device controls the rotational speeds of the compressor of the first stage among said plurality of compressors using a deviation of discharge pressure from a desired target pressure, and controls the rotational speed of each compressor on and after the second stage among said plurality of compressors based on the discharge pressure of the compressor in a stage before the each compressor or the suction pressure of the each compressor, using a pressure signal from said pressure detector provided for each compressor on and after the second stage among said plurality of compressors for detecting a discharge pressure of a compressor of a stage preceding the corresponding compressor or a suction pressure of the corresponding compressor. |
