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App. - 31

 

 

 
Appendix 4.21    Compressor sequential operation using ring counters 

This system provides pressure control using three compressors. 

A pressure shortage is detected by the three pressure switches. The number of 

compressors operating simultaneously depends on the degree of shortage. To equal 

the number of usages of each compressor, compressors are activated according to 

the set order. 

 

System configuration of compressor control 

 

A

B

C

Compressor

Pressure switch

PX1

PX2

PX3

Operating panel

MELSEC-Q

Sufficient 
pressure

Start button

Stop button

Pressure shortage "Major"

Pressure shortage "Medium"
Pressure shortage "Minor"

 

 
 

 

Start

PB0

Stop

PB1

Pressure switch

PX1

PX2

X0

X1

X2

X3

Input

Y70

Output

Y71

Y72

Y73

MC

A

MC

B

MC

C

Y74

Y75

Y76

Compressor A

Compressor B

Compressor C

Sufficient pressure

Pressure shortage "Minor"

Pressure shortage "Medium"

Pressure shortage "Major"

PX3

X4

MELSEC-Q