1. PREPARATIONS FOR INTRODUCING THE MACHINE
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[ 3 ] Calculating the approximate power consumption of compressor
(1) For oil-free reciprocating compressors, oil-free screw compressors, and turbo compressors
W = W1
×
n
×
[a + b (1 – a)]
(2) For oil injection screw compressors
W = W1
×
n
×
B’
(3) For compressors with their shaft input power known
W = Shaft input power
×
n [a + b (1 – a)]
Where
W:
Total power consumption (kWH)
W1: Motor power consumption (kWH per motor) =
(The motor efficiency can be assumed as 0.9.)
a:
Compressor load factor
(0.85 or less for reciprocating compressors, 0.90 or less for screw or turbo com-
pressors)
b:
Power ratio of unloaded compressor with relative to full-loaded compressor
0.20 to 0.25 for reciprocating compressors
0.20 to 0.40 for screw compressors
(The power ratio varies depending upon the compressor model and capacity
control method.)
0.20 to 0.25 for turbo compressors
n:
Number of compressors
B’:
Power ratio with relative to the ratio of the required air volume and compressor
discharge volume
NOTE:
Generally, the power consumption W1 should be calculated with the shaft power not with the
motor output. To obtain approximate power consumption, however, calculate it with the motor out-
put since the shaft power and motor efficiency vary depending upon motor models
Reference: Compressor manufacturers and types
Manufacturer
Lubricated type
Unlubricated type
Kobe Steel
HM type
ALE type
Hitachi
S and M types
DSP and SDS types
Atlas
GA type
ZR type
Mitsui Seiki
Z and ZV types
ZUV type
Motor rated output
Motor efficiency
