As the name suggests, a fixed speed air compressor operates at the same speed whenever it’s running. By design, it always draws the amount of power needed to meet the maximum compressed air demand, even if demand is less than maximum. Because the speed of the motor can’t change, whenever the demand for air changes, an air inlet valve adjusts to allow either more or less air to flow out.
In contrast, a Variable Speed Drive (VSD) air compressor can operate anywhere in the range between its minimum and maximum speed, and it automatically adjusts the speed so production of compressed air matches demand in real time. When demand increases, the motor speeds up. When demand decreases, the motor slows down. This capability saves energy because the compressor doesn’t have to run flat out whenever it’s on. You can think of VSD like the accelerator in a car, which allows you to vary the car’s speed according to road conditions, level of traffic and whether you’re in a hurry!
Sometimes, the most efficient compressed air solution combines one or more fixed speed compressors to provide a base load with one VSD compressor that “trims” to meet changes in demand. A system with multiple smaller compressors instead of one big compressor also provides redundancy that allows you to keep part of your facility operational when a compressor is offline for service or repair.
The optimal design of a compressed air system will reflect the specific needs of your processes, your facility and your approach to capital projects. To learn more about how Variable Speed Drive can address your needs, talk to an air system professional.