Compressed air is the life blood of manufacturing and processing, but the production of this critical commodity can account for more than 40% of a plant’s total electricity bill. Subsequently, energy is the most expensive component in the total cost of producing compressed air, making up over 80% of a compressor’s life cycle costs (LCC).
This was the problem Variable Speed Drive (VSD) compressor technology solved when it was launched 25 years ago and according to Atlas Copco, the company that pioneered it, VSDs remain the smart and most efficient solution for modern pneumatic processes with significant variations in compressed air demand that require increased and decreased air flow.
Most industrial users experience fluctuating air demand, increasing and decreasing between different processes, by time of day, by shift, on weekends, or by the time of the year. Instead of running at a fixed speed, the VSD compressor automatically adjusts its motor speed to perfectly match air production to air demand in real time.
This ability to vary its speed renders the VSD compressor much more energy efficient compared to a fixed-speed unit that can only run flat out even when during lower air demand. The greater the variation in air demand, the greater the potential savings VSD technology presents.
Atlas Copco said because the VSD compressor only runs when needed, it can save customers up to 50% on their energy bill, with the associated added value of low total cost of ownership and a rapid return on their investment in a VSD machine.
“It was not long before industry recognised the unparalleled advantages offered by Atlas Copco’s VSD technology compared to fixed-speed machines and today the company boasts a very large installed base in a wide variety of industries around the world,” the company said in a statement.
In addition to being able to operate within a much tighter pressure band than a fixed speed compressor can attain, the VSD machine can operate anywhere in the range between its minimum and maximum speed. When demand increases, the motor speeds up; when demand decreases, the motor slows down. It can be compared to a motor vehicle’s accelerator which allows the driver to vary speed according to road conditions.
Central to the VSD compressor’s success is the smart trio comprising the compressor motor, element and brain. The VSD adjusts the compressor’s speed (RPM) by means of an inverter. Instead of all the power going directly into a traditional AC motor that runs only at full capacity, the inverter provides the VSD compressor with the specific voltage required to meet demand, thus saving energy.
In terms of the element, VSD technology works best with rotary screw compressors as their flow rate and power consumption are virtually proportional to speed. As the motor adapts its speed to reflect demand, the rotary screw elements adapt in sync so the amount of compressed air delivered matches air demand.
Controlling the motor speed of an Atlas Copco VSD compressor is the brain i.e. the frequency inverter and the advanced on-board Elektronikon monitoring system. “With sensors continually measuring system pressure, the system adjusts the motor speed to meet the actual air demand, cutting the customer’s energy bill in half.”
Additional advantaged offered by a VSD compressor include start/stop ability under full system pressure which eliminates the need to unload, saving both time and energy. Additionally, no time is lost to idling, no blow-off losses occur in normal operations, coupled with more consistent, lower air system pressure minimise leakages.
Atlas Copco offers both VSD and fixed speed oil-free and oil-injected compressors in a wide range of sizes to ensure the most efficient compressed air solution for either fluctuating or consistent air demands respectively. Professional air audits are conducted by highly skilled Atlas Copco technicians to identify the most appropriate and optimal compressor and controls for a specific application.