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Permanent Magnet Variable Frequency Rotary Screw Air Compressors

Developed by parent company Kaishan Corporation, these revolutionary new rotary screw air compressors bring together an integrated systematic optimisation of the compressor unit, an advanced permanent-magnet motor and Kaishan two-stage technology to achieve outstanding energy efficiency.

This unique integrated combination is a game changer in the compressed air industry offering unsurpassed efficiency in compressors all the way down to 22kW. Southern Cross Air Compressors can now offer a superior range of advanced energy saving air compressors for virtually any industry application.

Energy costs contribute 85% of the cost of owning a screw compressor over it’s lifetime, therefore selecting a highly efficient screw compressor will have a significant impact on your businesses bottom line. The KHE Series have world class efficiency performance yet they are heavy-duty to ensure superior reliability also contributing to reduced maintenance costs.

Permanent Magnet Variable Frequency Rotary Screw Air Compressors

Two-stage air compressors are up to 20% more efficient than a typical single-stage compressor. As the compression ratio is spread over two distinct airends, customers get the benefits of both higher efficiency and longer bearing life.

The high efficiency of our newly developed two-stage screw air compressor units is the fundamental reason for our Permanent Magnet Variable Frequency air compressor’s class leading performance. Our unique package design and engineering offers obvious technological advantages including screw compressor unit efficiency, drive motor efficiency and overall unit control.

Rare earth material technology gives the permanent-magnet synchronised motors higher possible rotating speeds, wider operating parameters and increased energy efficiency. Within their wide operating speed range thebPermanent Magnet Variable Frequency rotary screw air compressors are able to maintain extremely high motor efficiency compared with those using conventional drive motors.

With an operating variable speed turndown range of 7:1 (conventional VS compressors 4:1), Kaishan’s Permanent Magnet Variable Frequency Rotary Screw Air Compressors operate at peak efficiency even with an 80% reduction in air output. It also offers far greater integrated control precision through an advanced PID control algorithm that provides highly stable supply pressures.

The fully enclosed oil-cooled Permanent Magnet  motor generates very little heat, resulting in a longer life. No cooling fan means significantly lower noise and less fan drag compared with conventional motors. The motor is heat resistant to 180 C and cannot be magnetised. With no external electrical excitation the motor maintains a power factor close to 1.

The precision speed adjustment capability (1/30,000) greatly reduces discharge fluctuations of the new range of air compressors.

Motor angular position sensors are not required, simplifying the system and improving both stability and reliability. Torque can be compensated at any angle within 360 to achieve perfect torque control and the utilisation of bus voltage is greater than 93%, which is much greater than conventional inverters.

Once a mains frequency screw air compressor deviates from its designated working specifications, its efficiency drops. Kaishan’s Permanent Magnet Variable Frequency technology is able to adjust the motor’s rotating speed according to demand variables at any time.

By regulating the volume of air output, the compressor is able to maintain maximum efficiency under all usage demands from 15 to 100%. Particularly in applications with widely fluctuating demand, Kaishan’s Permanent Magnet Variable Frequency type air compressors demonstrate a remarkable energy saving capacity as high as 50% over conventional types.


  • Complete control of air output to meet operating demand
  • Lower energy input for required air generation
  • Excessive part load energy consumption is significantly reduced Gradual increase in motor speed eliminates starting spikes and cost penalties
  • A steady system pressure is maintained, lowering system stress and overall air demand
  • Reduced artificial demand due to lower operating pressures
  • Reduced maintenance time and cost
  • Significantly lower noise levels