Gas compressor with a plurality of air realease systems each having an air release valve and an air regulating valve

A gas compressor that includes a compressor main body that compresses gas and discharges the compressed gas, an electric motor that supplies driving force to the compressor main body, a power conversion device that supplies predetermined frequency power to the electric motor, a plurality of air release valves disposed in a plurality of air release systems communicating with a discharge piping system to discharge the compressed gas to an atmospheric pressure environment, and a controller, the gas compressor performing unload operation of reducing, when a discharge pressure reaches a predetermined pressure, a load on the compressor main body by opening one of the air release valves, the gas compressor comprising:

• the plurality of air release systems each including at least one of the plurality of air release valves, and a plurality of pressure regulating valves provided on a downstream side of the at least one of the plurality of air release valves, respectively, and having an opening pressure and a closing pressure that are different between the plurality of pressure regulating valves, wherein the controller selects the at least one of the plurality of air release valves and performs the unload operation.