Showcase: Decrease Electrical Energy of Multiple Air Compressor Units


Invented an unexpensive method to reduce electrical energy usage in air compressor units inside our factory.


There are 3 compressor units 50HP, 30HP and 15 HP supply to the same air pipe line running around our facilities. The demand of pressurized air is vary during the day and night shift. Each compressor have its own pressure switch to cut-in and cut-out the unit independently. The compressors will be in "Load" at cut-in pressure and "Unload" at cut-out pressure, then motor will be stopped in "Standby" mode after "Unload" for 3 minutes. In "Standby" mode the compressor will "Load" again if the pressure is under the cut-in pressure. In "Unload" mode, the motor is still running but the the energy usage is about 50% of "Load" mode.



Cut-in and cut-out pressure of each air compressor is not coordinately set, so supply capacity power (HP) is unneccasary higher than the demand. Such as:
1. When there is small demand, the 50HP is still running instead of only the 15HP.
2. When there is medium demand, all of 3 compressor running in "Load" and "Unload" alternatively. Infact they will use lesser energy if the 30HP and 15 HP running with 50HP in "Standby" mode


The supply capacity power(HP) of the system should vary accordlingly to demand of air usage. We suggest that the supply capacity power(HP) of the system should be changed with the combination power of the 3 compressor as in the following table



1. To match the demand, one of possible solution might be using a single controller, with a pressure sensor to monitor pressure in the main pipe line, and 3 swicths to run a combination of compressors as in the Fig.2 . But the system will be complicate and expensive.
2. We come up with an inexpensive way to achive the target by invent a method to set up the cut-in and cut-out pressure of each individual pressure switch. Basically, we set the cut-in cut-out range of smallest compressor inside of the bigger ones. In this way, each air compressor will self controlly run the combination with their peers as their running cycle shown in Fig.3



For more understanding, please watch the video below




We have running this method with our air compressor system and it is working according to the plan. Anyway, there are a few points to mention here are:
1. Each air compressor and its connect pipe must be close to each others so there each pressure reading will be very much the same.
2. The compressor should have no leak around the pressure switch, otherwise the pressure reading will be incorrect.
3. The pressure switchs should be in the goood condition, so the reading will be accurate.
4. Due to there are a few different in reading by each pressure switch, we suggest a gap of cut-in and cut-out between compressors to no less than 0.3kg/cm2