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VSD vs fixed speed

A variable speed drive (VSD), speed-controller or frequency-controlled, compressor automatically adjusts its motor speed to the air demand. Its counterpart, fixed speed or “idling compressor”, or “load/unload compressor, is either on full throttle or off.

Compare it to a car: an “idling compressor” either drives 100 km per hour or not at all. That is fine if the application requires an either full load or no load compressed air supply. But most applications don’t, they have a fluctuating air demand and that is where a VSD compressor comes in the picture. A Variable Speed Drive compressor simply adjusts its motor and elements speed to match the demand.

The advantage is obvious: a variable speed drive only runs at the required speed, which saves considerable amounts of energy. When compared to an idling compressor, a VSD allows for energy savings of 35% on average, a GA VSD+ even 50% on average. And those savings do matter…

70% of a compressor’s cost is energy

The initial investment or maintenance costs of a compressor do not compare to its energy costs. Producing compressed air can account for more than 40% of a plant’s total electricity bill.


Variable speed drive has more benefits:

  • A VSD compressor can start/stop under full system pressure. There is no need to unload. This saves time and energy
  • No idling time lost, no blow-off losses in normal operations
  • With VSD, you avoid peak currents at start up and therefore also the penalties of most electricity companies
  • Thanks to a lower system pressure, system leakages are minimized