| 摘要 |
PROBLEM TO BE SOLVED: To prevent a delay of surging detection of a compressor, and to quickly detect the surging. SOLUTION: A sensor S is provided at a suction side or a discharge side of the compressor 1 to detect at least any one of pressure, flow quantity and flow speed. Output of the sensor W is commonly given to a first and a second first order time-lag circuits 11 and 12 forming a frequency and gain characteristic means 9. Output A and B of each first order time-lag circuit 11 and 12 is given to a subtracting means 13, and an output C expressing a difference between the output A and B is given to a first and a second level discrimination means 23 and 24 forming a variable counting means 22 and having a hysteresis characteristic, and output D and E of the level discrimination means 23 and 24 are counted by a counter 62 when a mutual judging circuit 9 judges that the output is mutually generated. When a count value X of the counter reaches the preset value X0 or more within the preset time W1 set by the timer 65, surging is decided to be generated.
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