For the production of compressed, liquid-cooled or dry-running air, screw compressors producing a given volume of air (star / delta coupling) or a variable volume (frequency controlled) are usually installed. To make your choice, all the conditions mentioned above must be taken into account. Depending on the case, one, two or more compressors may be the solution. To ensure an efficient supply of compressed air, the following points must be observed:
Supplied quantity The quantity supplied is the quantity of portable air compressor conveyed by a compressor in the connected compressed air network. It relates to the intake state of the compressor. The measure to compare different manufacturers is documented in ISO 1217, Annex C.
Specific power The ratio of the electrical power absorbed to the amount of air returned, for a given operating pressure, is referred to as the specific power (Figure 12).
Choice of efficient motors Depending on the required speed of the compressor, asynchronous motors with variable number of poles can be used.
Synchronous nominal speed (revolutions per minute):
2 poles with 3000 rpm
4 poles with 1500 rpm
6 poles with 1000 rpm
8 poles with 750 rpm
Motor efficiency classes from 0.12 to 1000 kW are defined in IEC 60034-30-1 (Figure 13). For low power up to 10 kW, efficiency gains between IE4 and IE1 are very high. For large powers of 100 to 1000 kW, the improvements are admittedly proportionally lower, but the decrease in losses in kW is however very important. Since 2015, only class IE3 (or IE2 with CF) or IE4 electric motors are allowed in Switzerland. The highest yields are obtained with permanent magnet or reluctance motors with electronic commutation.
Frequency converter
The use of frequency converters (CF) now serves as a universal solution for efficient installations. If we take into account the losses of the CF and their effect on the efficiency of the engines (3 to 5% of the power absorbed), this is not true in all cases. The use of a CF compressor is interesting in the following situations:
large consumption variations
low network volume
compared to a fixed speed compressor, idling times can be saved
For the production of compressed, liquid-cooled or dry-running air, screw compressors producing a given volume of air (star / delta coupling) or a variable volume (frequency controlled) are usually installed. To make your choice, all the conditions mentioned above must be taken into account. Depending on the case, one, two or more compressors may be the solution. To ensure an efficient supply of compressed air, the following points must be observed:
Supplied quantity The quantity supplied is the quantity of air conveyed by a compressor in the connected compressed air network. It relates to the intake state of the compressor. The measure to compare different manufacturers is documented in ISO 1217, Annex C.
Specific power The ratio of the electrical power absorbed to the amount of air returned, for a given operating pressure, is referred to as the specific power (Figure 12).
Choice of efficient motors Depending on the required speed of the compressor, asynchronous motors with variable number of poles can be used.
Synchronous nominal speed (revolutions per minute):
2 poles with 3000 rpm
4 poles with 1500 rpm
6 poles with 1000 rpm
8 poles with 750 rpm
Motor efficiency classes from 0.12 to 1000 kW are defined in IEC 60034-30-1 (Figure 13). For low power up to 10 kW, efficiency gains between IE4 and IE1 are very high. For large powers of 100 to 1000 kW, the improvements are admittedly proportionally lower, but the decrease in losses in kW is however very important. Since 2015, only class IE3 (or IE2 with CF) or IE4 electric motors are allowed in Switzerland. The highest yields are obtained with permanent magnet or reluctance motors with electronic commutation.
Frequency converter
The use of frequency converters (CF) now serves as a universal solution for efficient installations. If we take into account the losses of the CF and their effect on the efficiency of the engines (3 to 5% of the power absorbed), this is not true in all cases. The use of a CF compressor is interesting in the following situations:
large consumption variations
low network volume
compared to a fixed speed compressor, idling times can be saved
