Calculation standard of specific power of low-pressure screw air compressor The only criterion for judging whether a screw air compressor is energy-saving is "specific power". The specific power of a low-pressure air compressor first requires a complete understanding of the concept of its input power.
For example:
The parameters that need to be indicated on the motor nameplate of a screw low-pressure air compressor are (taking the conventional single-stage compressor 132kw model as an example: flow = 24m3/min, working pressure = 7Bar as an example):
Motor rated power (rated output power or rated shaft power): P = 132kwMotor efficiency (taking Huada Motor as an example): η = 94.7%Power factor: COSφ=0.892Service factor S.F=1.15 (Some manufacturers also use the service factor S.F=1.2)Based on the above parameters, we can know: The nominal rated input power of the motor of this machine (without considering the service factor and at full load):
P1 = (motor rated output power P ÷ motor efficiency η) = 132kw ÷ 94.7% = 139.39kw
The nominal rated input power of this machine (taking the service factor into account and at full load):
P2 = (main motor rated output power P ÷ main motor efficiency η) x (Service factor S.F-0.05) = (132kw ÷ 94.7%) x (1.15 – 0.05) = 153.33kw
(Note: In theory, a 5% margin should be considered when calculating the service factor, and the full calculation cannot be made)
The nominal specific power of the screw air compressor (at 7bar, considering the service factor and full load): PB1 = P2 ÷ 24 m3/min = 6.39kw/(m3/min)
If it is an air-cooled machine, the input power of the fan must also be considered. If the screw air compressor is an air-cooled machine, the rated power of the fan motor is 4.5kw, and the efficiency is 85%, then the input power consumption of the fan motor is:
PF = 4.5kw ÷ 85%= 5.29kw
Then the nominal total input power of the low-pressure screw air compressor machine (considering the fan power consumption and the service factor and full load): PZ = P2 + PF = 153.33 + 5.29 = 158.62 kw
The nominal specific power of the low-pressure screw air compressor air-cooled machine (at 7bar, considering the service factor and full load): PB2 = PZ ÷ 24 m3/min = 158.62 ÷ 24 = 6.61kw/(m3/min).