Atlas Copco Oil Lubricated Rotary Screw Air Compressors

Models GA15 VSD / GA18 VSD / GA22 VSD / GA26 VSD / GA30 VSD


Scope of Supply

The GA15 – 30 VSD Workplace, Variable Speed Drive, air cooled, silenced, rotary screw compressors are complete compressor packages that include the following equipment:

  • Rotary screw compression element
  • IP54 drive motor
  • High efficiency gearbox
  • Elektronikon MkV Graphic controller
  • Variable Speed Drive regulation
  • Integrated frequency inverter
  • Lubrication system
  • Aftercooler with integrated moisture separator
  • Zero loss electronic condensate drain
  • Radial cooling fan
  • First fill of lubricant
  • Steel base and acoustic enclosure

GA15-302  Compression & Drive

At the heart of the compressor is an Atlas Copco designed and manufactured compression element featuring asymmetric profile male and female rotors driven via a compact gearbox and matched Siemens IP54, totally enclosed fan-cooled inverter duty drive motor and Siemens frequency inverter.

The innovative high efficiency, maintenance free gearbox provides transmission efficiency equal to direct drive. An oversized motor drive end bearing integrated into the gearbox benefits from superior lubrication whilst the non drive end bearing is a greased sealed type. Motor bearing regreasing maintenance is therefore eliminated and bearing life is extended.

The combination of the high output compression element and high efficiency gearbox driven by a drive motor which is optimized for maximum efficiency across a wide speed range and the latest generation frequency inverter provides unrivalled compression efficiency and energy saving potential.  GA15-303

The GA VSD compressor reduces energy costs by:

    • Matching air output / energy consumption to system demand
    • Eliminating air wastage resulting from blowdown
    • Eliminating off load running energy consumption
    • A reduction in system working pressure, a 1 bar reduction gives a 7% reduction in energy consumption
    • Maintaining the system working pressure within +/- 0.1 bar
    • Soft starting with no current peaks enables unlimited motor starting
  • Flexible pressure selection from 4 and 13 bar with electronic gearing
  • Near unity power factor across the complete speed range

Flow Diagram

Air Flow

Ambient air filtered by a 3 micron intake filter(1), passes to the inlet arrester(2) and into the compression element(3). Lubricant is injected into the air and the air is compressed by the interaction of the male and female rotors. The air / oil mixture passes through a non return valve(4) to the oil reservoir(5) and oil separator element which removes the majority of the oil, providing compressed air with an oil content of less than 2 ppm. The air then passes through a minimum pressure valve(6) and is cooled by an air cooled aftercooler(7). The condensed moisture is removed by an low pressure drop integrated moisture separator and zero loss electronic condensate drain(9).


Lubricant contained in the oil reservoir(5) flows under differential pressure to a thermostatic bypass valve(13), air cooled oil cooler(12), high efficiency oil filter(14) and oil stop valve(15) before being injected into the compression element(3) where it cools, seals and lubricates the compression process. The high efficiency oil filter provides superior filtration to conventional filters resulting in cleaner lubricant. The thermostatic bypass valve(13) ensures that the compressor quickly reaches optimum operating temperature on start up and maintains temperature during periods of low load by allowing cold lubricant to bypass the oil cooler.


A low noise radial cooling fan provides air cooling to the oil cooler(7) and aftercooler(12), ensuring satisfactory running temperatures as well as ventilating the compressor enclosure and electrical cubicle.

Monitoring and Control

The compressor is fitted with the advanced Elektronikon MKV Graphic controller which monitors, controls and ensures safe operation of the unit. The controller incorporates a 3.5” colour display and provides advanced monitoring and control possibilities.

g7 control

An icon based menu navigation system simplifies set-up and operator interface.

The controller incorporates a web-server that provides remote, internet browser based, compressor status visualisation simply by connecting the controller to a local area network via the provided Ethernet port.

The controller also incorporates the following features:

  • Remote start / stop input
  • Remote load / unload input
  • General warning and shutdown outputs
  • Automatic restart after voltage failure
  • Timed starting and stopping
  • Dual pressure bands
  • Timed switching of pressure bands
  • Password protection of settings


The Elektronikon MkV Graphic controller accurately monitors pressure via a pressure transducer mounted at the compressor discharge and regulates the speed of the drive motor via a fully integrated frequency inverter to achieve the programmed system pressure. The result in an almost constant discharge pressure within a tolerance of +/- 0.1 bar.

The speed of the motor and compression element can be varied over a wide speed range enabling the GA VSD compressor to match to varying demands with maximum efficiency.

Safety and Protection

The control system will shutdown the compressor in the event of high temperatures and pressures and protects the unit from out of range operation. A safety valve fitted in the oil reservoir(4) protects the unit against over-pressurisation.

EMC and line filters, fitted as standard, ensure the machine is fully compliant with the Electro-Magnetic Compatibility directive 89/336/EEC and protect the supply network from harmonic effects.


The compressor is mounted on a free standing base with fork lift openings for easy handling and is enclosed in an acoustically lined polyester coated steel enclosure that reduces noise levels.

The enclosure features removable doors for easy access and a hinged door on the electrical cubicle.