Patent ID: 6755620
Filing Date: 2004-06-29
Classification: F04D,Y02B

Abstract:
A multi-stage variable speed compressor comprising:a plurality of compressors of which the rotational speeds are individually variable, said plurality of compressors being serially connected to each other so that the working fluid is compressed step by step; a pressure detector for detecting a discharge pressure of the compressor of the final stage among said plurality of compressors; a control device for controlling the rotational speeds of said plurality of compressors so that the discharge pressure of the compressor of said final stage among said plurality of compressors is set to a desired target pressure, wherein said control device receives a pressure signal detected by said pressure detector, calculates a deviation between said target pressure and said pressure signal, and individually controls the rotational speeds of said plurality of compressors using said deviation; and 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 in a stage preceding the corresponding compressor or a suction pressure of the corresponding compressor, wherein said control device controls the rotational speed of the compressor in the first stage among said plurality of compressors using said deviation, receives 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 in a stage preceding the corresponding compressor or a suction pressure of the corresponding compressor, and controls the rotational speed of each compressor on and after the second stage among said plurality of compressors based on a discharge pressure of the compressor in a stage preceding the corresponding compressor or a suction pressure of the corresponding compressor.