Compressed gas supply unit

A compressed gas supply unit, comprising:

• a plurality of scroll compressors, an inverter device allowing independent modulation of speeds of the respective scroll compressors, a merge pipe or a reservoir tank for collecting gas discharged from the plurality of scroll compressors, a pressure sensor detecting discharge pressure of the plurality of scroll compressors, and a controller controlling the inverter device for modulating the speeds of the respective scroll compressors,
• the controller including a speed range setting unit that sets an upper speed limit and a lower speed limit of the respective plurality of scroll compressors, a calculating unit that calculates a sum of speeds of the plurality of scroll compressors based on a load of the compressed gas supply unit, and a speed setting unit that allocates the calculated sum of speeds among the scroll compressors to set speeds for the respective scroll compressors, wherein
• when the sum of speeds calculated by the calculating unit is lower than a sum of upper speed limits of all the scroll compressors, the speed setting unit reduces the speed of a first scroll compressor by a first difference between the calculated sum of speeds and the sum of upper speed limits, and sets the speeds of the other scroll compressors to the upper speed limit, and when the first difference exceeds the upper speed limit of the first scroll compressor, the speed setting unit stops the first scroll compressor, and reduces the speed of a second scroll compressor by a difference between the first difference and the upper speed limit of the first scroll compressor.